They're funny forms of greetings (5)
I believe the answer is:
cards
'greetings' is the definition.
(card is a kind of greeting)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for cards that I've seen before include "Christmas post" , "They may be for playing or greeting" , "Odd people" , "52 in a pack" , "With which to play snap or patience, perhaps" .)