What is The Word for words which sound like they are e.g. slush, slimy, croak etc.?
The word you need is onomatopoeia and the derived adjective onomatopoeic: the formation of names or words from sounds that resemble those associated with the object or action to be named or those associated with the object or action to be named or that seem suggestive of its qualities: atishoo, babble, cuckoo, croak, ping-pong, sizzle.