In football games, I heard people use "卧草" for time-wasting actions near the end of a game. Is "卧草" a proper Chinese word? I did not find it in dictionaries.
However it does share the same pronunciation of
我肏, basically the Chinese equivalent of
卧草 became more popular due to widely existing profanity filtering on different internet platforms which mostly will filter out the origin term, while it also feels slightly more polite (Think about shoot vs. shit).
I would say 卧草 is a grammatically valid phase which means "lying on the grass". No dictionary would include it because if so, the dictionary would be too thick -- you can lie on anything.