random

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

• adjective Having no specific pattern, purpose, or objective: synonym: chance.
• adjective Mathematics & Statistics Of or relating to a type of circumstance or event that is described by a probability distribution.
• adjective Of or relating to an event in which all outcomes are equally likely, as in the testing of a blood sample for the presence of a substance.
• idiom (at random) Without a governing design, method, or purpose; unsystematically.

from The Century Dictionary.

• noun In mining, the direction of a rake-vein.
• noun A rushing, as of a torrent; an impetuous course; impetuosity; violence; force: especially with great, as in the phrase a great random, with great speed or force.
• noun A rush; spurt; gush.
• noun A continuous flow of words; a harangue.
• noun An indeterminate course or proceeding; hence, lack of direction, rule, or method; haphazard; chance: used only in the phrase at random—that is, in a haphazard, aimless, and purely fortuitous manner.
• noun The distance traversed by a missile; range; reach.
• Proceeding, taken, done, or existing at random; aimless; fortuitous; haphazard; casual.
• noun Something done or produced without definite method, or with irregular or haphazard effect.
• noun In dyeing, clouded yarn. See random yarn, under I.

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

• noun obsolete Force; violence.
• noun A roving motion; course without definite direction; want of direction, rule, or method; hazard; chance; -- commonly used in the phrase at random, that is, without a settled point of direction; at hazard.
• noun Distance to which a missile is cast; range; reach.
• noun (Mining) The direction of a rake-vein.
• adjective Going at random or by chance; done or made at hazard, or without settled direction, aim, or purpose; hazarded without previous calculation; left to chance; haphazard.
• adjective (Statistics) of, pertaining to, or resulting from a process of selection from a starting set of items, in which the probability of selecting any one object in the starting set is equal to the probability of selecting any other.
• adjective (Construction) of unequal size or shape; made from components of unequal size or shape.
• adjective in a manner so that all possible results have an equal probability of occurrence; for processes, each possible result is counted separately although the same type of result may occur more than once .
• adjective (Masonry) courses of stone of unequal thickness.
• adjective a shot not directed or aimed toward any particular object, or a shot with the muzzle of the gun much elevated.
• adjective (Masonry) stonework consisting of stones of unequal sizes fitted together, but not in courses nor always with flat beds.

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

• adjective Having unpredictable outcomes and, in the ideal case, all outcomes equally probable; resulting from such selection; lacking statistical correlation.
• adjective mathematics Of or relating to probability distribution.
• adjective computing Pseudorandom in contrast to truly random; mimicking the result of random selection.
• adjective Representative and undistinguished; typical and average; selected for no particular reason.
• adjective Apropos of nothing; lacking context; unexpected; having apparent lack of plan, cause, or reason.
• adjective colloquial Characterized by or often saying random things; habitually using non sequiturs.

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

• adjective lacking any definite plan or order or purpose; governed by or depending on chance