1) Directive at bridge 2) Do as others do 
In trick-taking games, following suit is the action of playing a card of the same suit as that of the leading suit. A player must follow suit if that player has cards of the leading suit in his hands. If not, he has the choice of playing a trump card to possibly win the game, or rough (waste) a different suit. It is also possible that the specific...
To play a card of the suit led.
In card games, follow suit means to play a card of the same suit as the previous card played in a trick.
[v] - do what someone else is doing
verb do what someone else is doing