The act of fishing by gently dipping or bouncing a lure on the water's surface, or bouncing something lightly.
From 'dap' (origin uncertain, possibly imitative of the dabbing motion), with the present participle suffix '-ing'; documented in fishing literature since the 1600s.
Dapping is so specialized that only anglers and fly-fishers really use the word today, but it's a perfect example of how working communities develop incredibly precise vocabulary for the tiny, essential details of their craft.
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