have another think coming
Definition from Wiktionary, the free dictionary
Alternative forms 
- have another guess coming, have another thing coming, have another think a-comin, have another thought coming
- To be deluded, to be mistaken; to need to rethink something one has determined; to need to reconsider one's plans or expectations.
- If you think you're going to marry my daughter, you have another think coming.
Usage notes 
- This expression is used as a rebuke, often in constructions similar to "If X thinks that Y, he/she has another think coming!" Sometimes the word got is included, in the familiar constructions has got and have got, as "(someone)'s got another think coming", "they've/you've got another think coming".
- The form to have another thing coming is often seen, and may have been aided by a mishearing of the /k/ of think blended with the /k/ of coming, making think sound like thing.
- Another common colloquial pronunciation in the US sounds like have another think a-comin'.
- 1901, Wallace Irwin, The Love Sonnets of a Hoodlum, VIII:
- My finish then less clearly do I see, / For lo ! I have another think a-coming.
- 1918, Jacob Marvin Rudy, Our Nation's Peril, page 132:
- ...and if you think just because we are at war I'm going to give my brains an opiate or send them away on a vacation, you got another think a comin'. I wasn't built that way.
- 1950, Conrad Richter, The Fields, page 72:
- But if she figured she could break him, she had another think a coming.
- 1967, Sylvia Wilkinson, A Killing Frost, page 47:
- I told them they had another think a-coming if they thought they could talk me down like they did Papa, and they could just pack themselves right off my...
- 1984, James Purdy, On Glory's Course, page 252:
- He had another think a-coming, that begrimed whoremonger!