Qt

• A quart, a measure of volume within traditional systems of units, equal to 2 pints
• A quarter, a unit of mass in Imperial units, equal to 2 stones or a quarter of an Imperial hundredweight; one quarter = 12.70058636 Kg.
• The Qt toolkit, cross platform graphical widget toolkit for the development of GUI computer programs
• "quiet", as in the (dated) slang expression "on the Q. T.", meaning "secretly"