Wiktionary
backfin
n. The rear fin of a fish.
Usage examples of "backfin".
She backfinned to hold still until all the echoes could come back to her, and in Nita’s mind the picture of the massive, fluted, narrowing pillar of stone got taller and taller, until she actually had to sing a soft note or two to deafen herself to it.
The buffet consisted of Beluga Malossol caviar, pate de campagne, smoked Scottish salmon, oysters on the half shell, backfin lump crabmeat, crudites with a shallot vinaigrette dressing, and Cristal champagne.