Pronunciation

change

Singular
stack

Plural
stacks

  1. (countable) A pile of something similar.
    There is a stack of books outside. Are those yours?

Plain form
stack

Third-person singular
stacks

Past tense
stacked

Past participle
stacked

Present participle
stacking

  1. When you stack something, you put something similar on top of one another to form a pile.
    I stacked up the books at one side.