Ma'anar ƙamus na kalmar "kwai-kwai" shine tsarin da dabbobi musamman dabbobin mata suke yin ƙwai a matsayin hanyar haifuwa. Yana nufin aikin ajiye ƙwai, waɗanda galibi ana haɗe su, daga jikin dabbar mace, sau da yawa zuwa wani waje na waje inda ƙwan ke iya tasowa da kyankyashe. Kwanin kwai wata hanya ce ta haifuwa a yawancin dabbobi, ciki har da tsuntsaye, dabbobi masu rarrafe, kwari, kifi, da monotremes (masu shayarwa kwai kamar platypus da echidna). A fagen kiwon kaji kuma, “kwai-kwai” na iya komawa ga samar da ƙwai da kaji ke yi don cin ɗan adam ko don ƙyanƙyashe kaji don aikin kiwon kaji.