'Clubbing' definitions:

Definition of 'clubbing'

noun

A condition in which the ends of toes and fingers become wide and thick; a symptom of heart or lung disease

From: GCIDE

Club \Club\ (kl[u^]b), v. t. [imp. & p. p. Clubbed (kl[u^]bd); p. pr. & vb. n. Clubbing.]
1. To beat with a club. [1913 Webster]
2. (Mil.) To throw, or allow to fall, into confusion. [1913 Webster]
To club a battalion implies a temporary inability in the commanding officer to restore any given body of men to their natural front in line or column. --Farrow. [1913 Webster]
3. To unite, or contribute, for the accomplishment of a common end; as, to club exertions. [1913 Webster]
4. To raise, or defray, by a proportional assesment; as, to club the expense. [1913 Webster]
To club a musket (Mil.), to turn the breach uppermost, so as to use it as a club. [1913 Webster]