pseudoprime

Noun

 * 1)  An integer that possesses at least one characteristic of a prime number without actually being prime. The characteristic is typically chosen to make such "false primes" very rare.
 * 2)  A Fermat pseudoprime; a composite integer n satisfying $$b^{n-1} \equiv 1 \pmod{n}$$ for some integer b such that b > 1.

Usage notes
In the sense of a Fermat pseudoprime, if no base is specified, base two is assumed. Integers that satisfy the congruence for a particular b are referred to as "pseudoprimes to base b" or "pseudoprimes to the base b."

Adjective

 * 1) Being such an integer.