enter

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

• intransitive verb To come or go into.
• intransitive verb To penetrate; pierce.
• intransitive verb To introduce; insert.
• intransitive verb To become a participant, member, or part of; join.
• intransitive verb To gain admission to (a school, for example).
• intransitive verb To cause to become a participant, member, or part of; enroll.
• intransitive verb To embark on; begin.
• intransitive verb To make a beginning in; take up.
• intransitive verb To write or put in.
• intransitive verb To place formally on record; submit.
• intransitive verb To go to or occupy in order to claim possession of (land).
• intransitive verb To report (a ship or cargo) to customs.
• intransitive verb To come or go in; make an entry.
• intransitive verb To effect penetration.
• intransitive verb To become a member or participant.
• noun A key on a keyboard or keypad used to enter or confirm a command or other textual input.

from The Century Dictionary.

• A prefix immediately of French origin, but ultimately of Latin origin, signifying ‘between’: same as inter-.
• To come or go into; pass into the inside or interior of; get into, or come within, in any manner: as, to enter a house, a harbor, or a country; a sudden thought entered his mind.
• To penetrate into; pass through the outer portion or surface of; pierce: as, the post entered the soil to the depth of a foot.
• To go inside of; pass through or beyond: as, I forbid you to enter my doors.
• To begin upon; make a beginning of; take the first step in; initiate: as, the youth has entered his tenth year; to enter a new stage in a journey.
• To engage or become involved in; enlist in; join; become a member of: as, to enter the legal profession, the military service or army, an association or society, a university, or a college.
• To initiate into a business, service, society, or method; introduce.
• To insert; put or set in: as, to enter a wedge; to enter a tenon in a mortise; to enter a fabric to be dyed into the dye-bath.
• To set down in writing; make a record of; enroll; inscribe: as, the clerk entered the account or charge in the journal.
• To cause to be inscribed or enrolled; offer for admission, reception, or competition: as, to enter one's son or one's self at college; to enter a friend's name at a club; to enter a horse for a race.
• To report at the custom-house, as a vessel on arrival in port, by delivering a manifest: as, to enter a ship or her cargo.
• In law: To go in or upon and take possession of, as lands. See entry.
• To place in regular form before a court; place upon the records of a court: as, to enter a writ, an order, or an appearance.
• To set on game; specifically, of young dogs, to set on game for the first time.
• To make an entrance, entry, or ingress; pass to the interior; go or come from without inward: used absolutely or with in, into, on, or upon. See phrases below.
• Specifically To appear upon the stage; come into view: said of personages in a drama, or of actors: as, enter Lady Macbeth, reading a letter.
• To begin; make beginning.
• To engage in: as, to enter into business.
• To be or become initiated in; comprehend.
• To deal with or treat fully of, as a subject, by way of discussion, argument, and the like; make inquiry or scrutiny into; examine.
• To be an ingredient in; form a constituent part in: as, lead enters into the composition of pewter.
• To begin to treat or deal with, as a subject, by way of discussion, argument, and the like.
• See inter.
• An obsolete form of entire.

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

• intransitive verb To go or come in; -- often with in used pleonastically; also, to begin; to take the first steps.
• intransitive verb To get admission; to introduce one's self; to penetrate; to form or constitute a part; to become a partaker or participant; to share; to engage; -- usually with into; sometimes with on or upon