Waggish means that someone is humorous or witty — the kind of person who'd keep you in stitches all night if you sat next to one at a party.
Despite the wag part of the word, waggish does not refer to the characteristic tail flick that our canine friends exhibit when they are happy to see us. Instead, waggish is an adjective and actually describes someone who is a wag — the kind of hilarious person who keeps you entertained with witty stories and jokes.