Random Number Generator

A process used to generate an unpredictable series of numbers. Also called a Random bit generator (RBG). 

See NIST SP 800-57 Part 1 Rev. 4 under Random number generator (RNG) for more information. 
 
A process that is invoked to generate a random sequence of values (usually a sequence of bits) or an individual random value. 

See IETF RFC 4949 Ver 2 for more information. 
 
Produces a sequence of zero and one bits that is random in the sense, that there is no way to describe its output that is more efficient than simply listing the entire string of output. There are two basic classes: deterministic and non-deterministic. A deterministic RNG (also known as a pseudorandom number generator) consists of an algorithm that produces a sequence of bits from an initial value called a seed. A non-deterministic RNG produces output that is dependent on some unpredictable physical source that is outside human control, such as thermal noise or radioactive decay. 

See NIST SP 800-57 Part 2 under Random Number Generator (RNG) for more information. 
 
A mechanism that purports to generate truly random data. 

See NIST SP 800-22 Rev. 1a under Random Number Generator (RNG) for more information.