Dragan,

These may not be the same definitions that the original poster was referring to but I have seen these things defined as;

Recursion: A program calling itself as in ...

* Recurse.prg
DO Something
IF Whatever
   DO Recurse
ENDIF

Reentrancy: A program that may be called by another while it is already in the calling stack;

* Reenter.prg
DO Something


* Something.prg
DO someother
IF Whatever 
   DO Reenter
ENDIF