transcendental (thing)

A transcendental number is a number that cannot be expressed as a root of a polynomial equation with rational coefficients. (Oppose algebraic).

Some notable transcendental numbers:

• Pi
• e
• e^(Pi)
• 2^Sqrt(2)
• sin(1)
• Gamma(1/3)

Interestingly (to me, anyhow), although e^Pi is known to be transcendental, it is not known whether or not e^e, Pi^e, or Pi^Pi are transcendental.

Reference: Eric Weisstein's World of Mathematics
http://mathworld.wolfram.com/TranscendentalNumber.html