Chromatic

A scale of pitches rising in semitone steps.

source" http://www.soundonsound.com/information/Glossary.php#C

Semitone:

Short interval which in the western "equal tempered" system of tuning corresponds to one twelfth of an octave. Sometimes known in the US as a "half step".

source: http://www.zonicweb.net/music/musictechnologydictionary2.htm