Definition of "reentrant"

reentrant

/ɹiːˈɛntɹənt/

adjective
not comparable
1. Reentering; pointing inward.
2. (programming, of a mutex) Such that the corresponding lock can be reacquired by the locking thread.
3. (programming) That may be executed more than once at a time either by different threads, or because of recursion.
  Quotations
  Actor serialization […] might even lead to possible deadlock. To mitigate that risk, there's an important exception to actor serialization: actors are reentrant. This means that when an actor itself says await, then while the actor's code is waiting, its members can be accessed from outside the actor using await.
  2021, Matt Neuburg, iOS 15 Programming Fundamentals with Swift, 8th edition, O'Reilly, page 386
4. (aeronautics, of a part of a rocket) Designed to return to the Earth's atmosphere.
5. (physiology) Of or pertaining to reentry (in the heart);
6. (music, of a ukulele or similar instrument) Having the strings not ordered according to pitch (having a re-entry).
noun
plural reentrants
1. An angle or part that reenters itself.
2. One who enters (the labour market, etc.) again.
3. (geography) A valley between a pair of parallel ridges.