'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
  • Flip-flap \Flip"-flap`\, n. [See Flip, and Flap.] The repeated stroke of something long and loose. --Johnson. [1913 Webster]

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]