A liquid verb is any verb that has a liquid letter for its last letter. The liquid letters are λ ρ μ ν. They are called “liquid” because to pronounce them, the speaker forces air either around the tongue (λ, ρ) or through the nose (μ, ν). See BBG 20.13,14,15 or this video.
Note: the tense formative for aorist active verbs is σα. For aorist active liquid verbs it is simply α. (BBG 20.11)
