An RBG that always has access to an entropy source and (when working properly) produces output bitstrings that have full entropy. Often called a True Random Number (or Bit) Generator. (Contrast with a deterministic random bit generator).
Source(s):
NIST SP 800-90A Rev. 1
under Non-Deterministic Random Bit Generator (Non-deterministic RBG) (NRBG)
An RBG that always has access to an entropy source and (when working properly) produces outputs that have full entropy (see SP 800-90C). Also called a true random bit (or number) generator (Contrast with a DRBG).
Source(s):
NIST SP 800-90B