Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
flap [flæp] n (of envelope) отворо́т; (of pocket) кла́пан; (of jacket) пола́#
vt (arms) маха́ть*(impf) +instr ; (wings) хло́пать (impf) +instr
vi (sail, flag) колыха́ться*(impf) (inf)(also: be in a flap) волнова́ться (impf)
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.