1) Gapped scale 2) Relating to a scale 
A five note scale
[adj] - relating to a pentatonic scale
Pertaining to scales of 5 notes to the octave, in particular 1-2-3-5-6 of the major scale. Pentatonic melodies are typical of much indigenous music around the world, and these scales are also an important part of the modern Jazz sound. Pentatonic melodies and patterns were especially typical of Jazz and fusion in the seventies.
adjective relating to a pentatonic scale
a five-tone scale (e.g., the black keys of the piano).