the suit in which the most cards are held in a hand.
(in bridge) a suit in which four or more cards are held in a hand.
2.
the quality, activity, endeavor, etc., in which one excels:
Diligence is his long suit.
Origin
1875-80
Examples from the web for long suit
Truth is not their long suit either and deafness to reason is endemic.
British Dictionary definitions for long suit
long suit
noun
1.
the longest suit in a hand of cards
a holding of four or more cards of a suit
2.
(informal) an outstanding advantage, personal quality, or talent
Idioms and Phrases with long suit
long suit
One's strong point or advantage, as in Organizing has never been Nancy's long suit. This expression alludes to whist, bridge, and other card games in which holding numerous cards in a single suit may convey a strong advantage. [ c. 1900 ]