a condition in which the ends of toes and fingers become wide and thick; a symptom of heart or lung disease
"After months of severe smoking, the doctor noticed clubbing on his fingertips as an early warning sign of lung damage."
An instance of using a club.
"The detective noticed fresh gouge marks on the wall, confirming that the suspect had been caught up in a violent struggle involving a heavy iron club."
present participle of club
"The heavy rain caused him to stumble as he was clubbing along the muddy path home."