The sound of water or liquid gently splashing or moving against something, or an animal drinking by scooping liquid with its tongue.
From Middle English 'lappen,' possibly imitative of the sound itself. The meaning of an animal drinking comes from the lapping motion and sound of tongues in water.
Cats and dogs can't suck like humans do—they lap by curling their tongues to scoop water, which is why they look so messy compared to how they drink from bowls versus fountains.
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