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1. To gather or accumulate into a large amount. I'm sorry, I'm going to be late for dinner tonight—things have really been stacking up at work all day. With so many bills stacking up, I don't know how we're going to get through Christmas.
2. To compare to or rank against someone or something similar. Well, how does your new car stack up against your old one? He's obsessed with how he stacks up compared to my previous boyfriends.
3. To be logical or believable. I listened to Jill's explanation, but I'm still skeptical—something just doesn't stack up. I've been staring at this equation for over an hour, but it just isn't stacking up for me.
stack something up
to make a stack of things. (Also without the up.) Where should I stack them up? Please stack up these boxes.
[for something] to accumulate, as in stacks. Your work is stacking up. You will have to work late to finish it. I hate to let my work stack up. I have to do it sooner or later.
1. Measure up, equal, as in Their gift doesn't stack up against mine. This usage alludes to piling up one's chips at poker, and comparing them to those of the other players. [Early 1900s]
2. Make sense, seem plausible, as in Her explanation just doesn't stack up. Also see add up, def. 2.
1. To arrange something in a stack; pile something: I stacked up the magazines in orderly piles. Don't leave newspapers all over the floor; stack them up neatly.
2. To form into or as if into a stack; accumulate: I've been away for two weeks, and my mail is stacking up.
3. To equal or be of similar quality: The salary and benefits at this company don't stack up against those offered by larger companies.
4. To rank against one another; bear comparison: We sent our critic out to see how the local restaurants stack up.
5. To make sense; add up: The story he gave the police was full of contradictions—it just didn't stack up.
6. To direct or cause some aircraft to circle at different altitudes while waiting to land: The control tower stacked up the planes until the runway could be cleared. The controllers stacked the planes up because only one runway was open.