A deterministic computational process that has one or more inputs called "seeds", and it outputs a sequence of values that appears to be random according to specified statistical tests. A cryptographic PRNG has the additional property that the output is unpredictable, given that the seed is not known.
CNSSI 4009-2015 under pseudorandom number generator from IETF RFC 4949 Ver 2 - Adapted
See Deterministic Random Bit Generator.
NIST SP 800-90A Rev. 1 under Pseudorandom Number Generator