(verb-used with or without an object) When your woman or female gets out of line, disrespects you or your homeboys, or just needs a good ol' slapping. You give her a hard but not bruising slap on the vagina, try to miss the clit, as too light a slap may in fact cause her pleasure, and that is not the goal of a dewlappy slappy.
Allan: Sandra said my tie was ugly.
Steve: Did you give her a good dewlappy slappy.
Allan: Right on the va-jay-jay.