adj; not good or talented at anything, both military and civil field (art or martial art)
Definitions (粵典–words.hk)
語句、俚語
歇後語：「文又唔得，武又唔得」；「文」係「聞」嘅諧音（指屎坑、屎氹太臭，聞唔落），而「武」係「舞」嘅諧音（指屎坑、屎氹太窄，舞唔到關刀）。 part of a sandwich pun to imply a person lacking in both intellectual and martial capacity; literally: "crapper guandao"
參看
屎氹關刀
Definitions (Wiktionary)
phrase, Cantonese, idiomatic
to lack ability and be useless. Short for 屎坑關刀——文又唔得，武又唔得／屎坑关刀——文又唔得，武又唔得.