A diminished arpeggio is a three note broken chord with a numerical formula of T/1-♭3-♭5 played as individual notes in sequence, the same as you would play a scale.
Diminished arpeggio profile
|Notation formula (key of C)||C-E♭-G♭-C/1|
Diminished arpeggio patterns
Diminished arpeggio audio sample(s)
|C Diminished arpeggio pattern #4|