Above boardMeaning : Honest and open
Usage : His financial dealings were always above board
At sixes and sevensMeaning : In a disordered manner
Usage : Mrs. Sharma is at sixes and sevens since the death of her husband.
Alpha and omegaMeaning : The beginning and the end
Usage : He was forced to learn the alpha and omega of corporate law in order to even talk to the lawyers.
An acid testMeaning : A critical test
Usage : The acid test for the product will be whether people actually but it.
At a snail's paceMeaning : very slowly
Usage : Things are moving along at a snail's pace here, but we'll finish on time - have no fear
To burn one's boatsMeaning : Go bank on a decision
Usage : The committee has finally decided to burn its boats.
A bolt from the blueMeaning : Something unexpected
Usage : The news that Mr. and Mrs. Avtaar were getting a divorce struck all their friends as a bolt from the blue.
A burning questionMeaning : An important topic
Usage : There's a burning question that needs to be answered: Why did you leave your wife only after one month of your wedding?
A big gunMeaning : An important person
Usage : She's big gun in city politics.
A brown studyMeaning : Dreaming
Usage : Come out of your brown study, Live in the practical world.
Take one to taskMeaning : Rebuke
Usage : His performance during mid-terms has not been good. His father will not take him to task.
Gain groundMeaning : Become popular
Usage : Amitabh bachchan actually gained ground after giving 7 flops.
Turn over a new leafMeaning : Change for the better
Usage : You should turn over a new leaf to move ahead in your life.
In the nick of timeMeaning : Just at the last moment
Usage : If you continue to finish your projects in the nick of time, you cannot survive in the industry in long run.
With a high handMeaning : Oppressively
Usage : His master has been getting all things done through him with a high hand.