'mix up' definitions:

Definition of 'mix up'

From: WordNet
verb
Assemble without order or sense; "She jumbles the words when she is supposed to write a sentence" [syn: jumble, confuse, mix up]
verb
Cause to be perplexed or confounded; "This problem stumped her" [syn: stump, mix up]

Definition of 'mix up'

From: GCIDE
  • mix up \mix up\ n.
  • 1. To confuse the identities of (two or more objects); to mistake (one object for another); as, at the family gathering he mixed up his two nieces, to their great amusement. [PJC]
  • 2. To mix together; -- usually implying a mistake, whether done intentionally or unintentionally; as, the mixed up this year's receipts with last year's, and it took hours to find the right ones. [PJC]