an accumulation of jobs not done or materials not processed that are yet to be dealt with (especially unfilled customer orders for products or services)
(bridge) a playing card with a value sufficiently high to insure taking a trick in a particular suit; "if my partner has a spade stopper I can bid no trump"
close or secure with or as if with a stopper; "She stoppered the wine bottle"; "The mothers stoppered their babies' mouths with pacifiers"
shut out from view or get in the way so as to hide from sight; "The thick curtain blocked the action on the stage"; "The trees obstruct my view of the mountains"
hinder or prevent the progress or accomplishment of; "His brother blocked him at every turn"
an obstruction that stands in the way (and must be removed or surmounted or circumvented)
something immaterial that stands in the way and must be circumvented or surmounted; "lack of imagination is an obstacle to one's advancement"; "the poverty of a district is an obstacle to good education"; "the filibuster was a major obstruction to the success of their plan"