by a very small amount.

Last time she raced against the Brazilian she won by a whisker.

He missed the goal by a whisker.

• a kept woman
• a kerb-crawler
• a kick in the butt
• a kick in the teeth
• a kick up the arse
• a kick up the backside
• a king's ransom
• a kissing cousin
• a knight in shining armor
• a knight in shining armour
• a knocking shop
• a know-all
• a knuckle sandwich
• a labor of love
• a labour of love
• a lady-killer
• a lager lout
• a lame duck
• a lard-arse
• alarm bells start to ring
• a last hurrah
• a latchkey child
• a latchkey kid
• a laugh a minute
• a laughing stock