Juvenile, the Tritone is also called the "flat 5th". You could also call it an "augmented 4th". (But I think that I would say "flat 5" if I was talking about it.)
Fun with Tritones!
1. Consider the blues scale (in C)
C Eb F Gb G Bb C
Play this fast any you will see why we play flat fives.
2. Another interesting feature of this scale, for a singer or an instrument that is not restricted the equal tempered scale, is that the Eb is actually (normally) sounded as the mean of the Eb and E (half-way between them). Play the scale again, on a piano, and strike the Eb and E at the same time.
3. Wiping notes
Consider the triad C E G
Get there by quickly playing C Eb Gb, use the same fingers and "wipe" to
C E G.