'Flip-flap' definitions:
Definition of 'flip-flap'
From: WordNet
adverb
With repeated strokes and noise; "something going flip- flap in the night"
Definition of 'Flip-flap'
From: GCIDE
Definition of 'Flip-flap'
From: GCIDE
- Flip-flap \Flip"-flap`\, adv. With repeated strokes and noise, as of something long and loose. --Ash. [1913 Webster]