A minor 7th flat five chord is created by flattening the 5th degree of any minor 7th chord. E.g. a Cm7b5 chord contains the notes C, Eb, Gb and Bb (1, b3, b5 and b7). Because of the flattened 5th degree, this chord is sometimes referred to as a half diminished. Here are some common moveable minor 7th flat five chord shapes.
Minor 7b5 chords are commonly used in minor keys.