concurrent

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Happening at the same time as something else. See Synonyms at contemporary.
2. adj. Operating or acting in conjunction with another.
3. adj. Meeting or tending to meet at the same point; convergent.
4. adj. Being in accordance; harmonious.

Century Dictionary and Cyclopedia

1. Meeting in a point; passing through a common point.
2. Concurring, or acting in conjunction; agreeing in the same act; contributing to the same event or effect; operating with; coincident.
3. Conjoined; joint; concomitant; cördinate; combined.
4. n. One who concurs; one agreeing with or like another in opinion, action, occupation, etc.
5. n. In English law, specifically, one who accompanies a sheriff's officer as witness or assistant.
6. n. That which concurs; a joint or contributory thing.
7. n. One having an equal claim or joint right.
8. n. A rival claimant or opponent; a competitor.
9. n. The day, or in the case of leap-year the two days, required to be added to fifty-two weeks to make the civil year correspond with the solar: so called because they concur with the solar cycle, whose course they follow.

Wiktionary

1. adj. Happening at the same time; simultaneous.
2. adj. Belonging to the same period; contemporary.
3. adj. Running alongside one another on parallel courses; moving together in space.
4. adj. computing Involving more than one thread of computation.
5. n. One who, or that which, concurs; a joint or contributory cause.
6. n. One pursuing the same course, or seeking the same objects; hence, a rival; an opponent.
7. n. One of the supernumerary days of the year over fifty-two complete weeks; so called because they concur with the solar cycle, the course of which they follow.

GNU Webster's 1913

1. adj. Acting in conjunction; agreeing in the same act or opinion; contributing to the same event or effect; coöperating.
2. adj. Conjoined; associate; concomitant; existing or happening at the same time.
3. adj. Joint and equal in authority; taking cognizance of similar questions; operating on the same objects.
4. adj. (Geom.) Meeting in one point.
5. n. One who, or that which, concurs; a joint or contributory cause.
6. n. One pursuing the same course, or seeking the same objects; hence, a rival; an opponent.
7. n. (Chron.) One of the supernumerary days of the year over fifty-two complete weeks; -- so called because they concur with the solar cycle, the course of which they follow.

WordNet 3.0

1. adj. occurring or operating at the same time