tangent

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

• noun A line, curve, or surface meeting another line, curve, or surface at a common point and sharing a common tangent line or tangent plane at that point.
• noun The trigonometric function of an acute angle in a right triangle that is the ratio of the length of the side opposite the angle to the length of the side adjacent to the angle.
• noun A sudden digression or change of course.
• noun Music An upright pin in a keyboard instrument, especially in a clavichord, that rises to sound a string when a key is depressed and stops the string at a preset length to set the pitch.
• adjective Making contact at a single point or along a line; touching but not intersecting.

from The Century Dictionary.

• noun One of the keys or finger-levers of the hurdy-gurdy.
• noun In railroading, a straight piece of track beginning and ending at a curve.
• To bear or hold the relation of a tangent to.
• Touching; in geometry, touching at a single point: as, a tangent line; curves tangent to each other.
• noun In geometry: A straight line through two consecutive points (which see, under consecutive) of a curve or surface.
• noun The length cut off upon the straight line touching a curve between the line of abscissas and the point of tangency.
• noun In trigonometry, a function of an angle, being the ratio of the length of one leg of a right triangle to that of the other, the angle opposite the first leg being the angle of which the tangent is considered as the function.
• noun In the clavichord, one of the thick pins of brass inserted in the back ends of the digitals so that the fingers should press them against the strings, and produce tones.
• noun Any method of drawing a tangent to a curve.

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

• noun (Geom.) A tangent line curve, or surface; specifically, that portion of the straight line tangent to a curve that is between the point of tangency and a given line, the given line being, for example, the axis of abscissas, or a radius of a circle produced. See Trigonometrical function, under function.
• noun the logarithm of the natural tangent of an arc.
• noun a decimal expressing the length of the tangent of an arc, the radius being reckoned unity.
• noun (Elec.) a form of galvanometer having a circular coil and a short needle, in which the tangent of the angle of deflection of the needle is proportional to the strength of the current.
• noun the natural tangent of the arc subtending or measuring the angle.
• noun a right line, as ta, touching the arc of a circle at one extremity a, and terminated by a line ct, passing from the center through the other extremity o.
• adjective (Geom.) Touching; touching at a single point.
• adjective (Geom.) a plane which touches a surface in a point or line.
• adjective (Gun.) a kind of breech sight for a cannon.
• adjective (Mach.) an endless screw; a worm.

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

• noun geometry A straight line touching a curve at a single point without crossing it there.
• noun trigonometry In a right triangle, the ratio of the length of the side opposite the angle to the length of the side adjacent to the angle. Symbols: tan, tg
• noun A topic nearly unrelated to the main topic, but having a point in common with it.
• noun A small metal blade by which a clavichord produces sound.
• adjective geometry Touching a curve at a single point but not crossing it at that point.
• adjective Of a topic, only loosely related to a main topic.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a straight line or plane that touches a curve or curved surface at a point but does not intersect it at that point
• noun ratio of the opposite to the adjacent side of a right-angled triangle