What is "stack up"

vb. 1 (context transitive English) To put into a stack 2 (context intransitive English) to pile up; to accumulate 3 (context idiomatic transitive English) To put a group of abstract things together. 4 To compare with something; to measure up. (Often used with "against", "among")

v. arrange into piles or stacks; "She piled up her books in my living room" [syn: pile up, heap up]