adjective

1. Reentering; pointing inward.

2. (of a mutual exclusion mechanism) Such that the corresponding lock can be reacquired by the locking thread.

   “The global interpreter lock of the embedded scripting engine is not reentrant.”

3. That may be executed more than once at a time either by different threads, or because of recursion.

   “Global variables must not be altered by reentrant code.”