Noun
melodic minor scale (plural melodic minor scales)
(music) a type of minor scale with the 3rd note lowered by one semitone when the scale is played ascending, and the 3rd, 6th, and 7th notes lowered by one semitone when descending, with the interval patterns:
tone - semitone - tone - tone - tone - tone - semitone, and
tone - semitone - tone - tone - semitone - tone - tone
Starting on the note C, this produces a scale with the notes C, D, E♭, F, G, A, B, C ascending and C, D, E♭, F, G, A♭, B♭, C descending.
Traditionally, music theorists have called these two options the ascending melodic minor scale (also known as heptatonia seconda, jazz minor scale or Ionian 3) and descending melodic minor scale respectively. Source: Internet