minor

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Lesser or smaller in amount, extent, or size.
• adjective Lesser in importance, rank, or stature.
• adjective Lesser in seriousness or danger.
• adjective Law Not having reached legal adulthood.
• adjective Chiefly British Relating to or being the younger or junior of two pupils with the same surname.
• adjective Of or relating to a secondary area of academic specialization.
• adjective Logic Dealing with a more restricted category.
• adjective Relating to or being a minor scale.
• adjective Less in distance by a half step than the corresponding major interval.
• adjective Based on a minor scale.
• noun One that is lesser in comparison with others of the same class.
• noun Law One who has not reached legal adulthood.
• noun A secondary area of specialized academic study, requiring fewer courses or credits than a major.
• noun One studying in a secondary area of specialization.
• noun A minor premise.
• noun A minor term.
• noun Music A minor key, scale, or interval.
• noun Sports The minor leagues of a sport, especially baseball.
• intransitive verb To pursue academic studies in a minor field.

from The Century Dictionary.

• Smaller (than the other); less; lesser: applied definitively to one of two units or parts, and opposed to major or greater: as, the minor axis of an ellipse: the minor premise of a syllogism; the minor part of an estate.
• Smaller than others; of inferior rank or degree; lower; hence, small; inconsiderable; not capital, serious, or weighty: as, the minor officers of government; a minor canon; the minor points of an argument; minor faults or considerations.
• Under age.
• In music: Of intervals, less; shorter; smaller (as compared with major intervals).
• Of tonalities and scales, characterized by a minor third and also usually by a minor sixth, and often a minor seventh: opposed to major. See key, tonality, scale
• of triads and chords generally, characterized by a minor third between the lowest and the next to the lowest tones: opposed to major. See triad, and chord
• Of modes, characterized by the use of a minor tonality and of minor cadences: as, the piece is written throughout in the minor mode: opposed to major. See major
• noun A person of either sex who is under age; one who is of less than the legal age for the performance of certain acts; one under the authority of parents or guardians, because of not having reached the age at which the law permits one to make contracts and manage one's own property; an infant in the legal sense
• noun In logic, the minor term, or the minor premise. See I.
• noun In music, the minor mode or a minor tonality or minor chord taken absolutely.
• noun [capitalized] A Franciscan friar; a Minorite: so called from a name of the Franciscan order, Fratres Minores, or Lesser Brethren. Also called Friar Minor.

from the GNU version of the Collaborative International Dictionary of English.

• noun A person of either sex who has not attained the age at which full civil rights are accorded; an infant; in England and the United States, one under twenty-one years of age.
• noun (Logic) The minor term, that is, the subject of the conclusion; also, the minor premise, that is, that premise which contains the minor term; in hypothetical syllogisms, the categorical premise. It is the second proposition of a regular syllogism, as in the following: Every act of injustice partakes of meanness; to take money from another by gaming is an act of injustice; therefore, the taking of money from another by gaming partakes of meanness.
• noun A Minorite; a Franciscan friar.
• adjective Inferior in bulk, degree, importance, etc.; less; smaller; of little account.
• adjective (Mus.) Less by a semitone in interval or difference of pitch.
• adjective (Geog.) the Lesser Asia; that part of Asia which lies between the Euxine, or Black Sea, on the north, and the Mediterranean on the south.
• adjective (Mus.) that mode, or scale, in which the third and sixth are minor, -- much used for mournful and solemn subjects.
• adjective (Eccl.) the rank of persons employed in ecclesiastical offices who are not in holy orders, as doorkeepers, acolytes, etc.
• adjective (Mus.) The form of the minor scale is various. The strictly correct form has the third and sixth minor, with a semitone between the seventh and eighth, which involves an augmented second interval, or three semitones, between the sixth and seventh, as, 6/F, 7/G♯, 8/A. But, for melodic purposes, both the sixth and the seventh are sometimes made major in the ascending, and minor in the descending, scale, thus: -- [1913 Webster] [1913 Webster] See Major.
• adjective (Logic) the subject of the conclusion.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Of little significance or importance.
• adjective music Of a scale which has lowered scale degrees three, six, and seven relative to major, but with the sixth and seventh not always lowered
• adjective music being the smaller of the two intervals denoted by the same ordinal number
• noun A person who is below the legal age of responsibility or accountability.
• noun A subject area of secondary concentration of a student at a college or university, or the student who has chosen such a secondary concentration.
• noun mathematics determinant of a square submatrix
• verb To choose or have an area of secondary concentration as a student in a college or university.