What is the meaning of butted head?

[Miky]

English Language Tests, Intermediate level

ESL/EFL Test #279 "English Slang Idioms (1)", question 6

Jim and I ......... heads when we first met, but we are good friends now.

(a) rubbed
(b) slapped
(c) butted
(d) covered

English Language Tests, Intermediate level

ESL/EFL Test #279 "English Slang Idioms (1)", answer 6

Jim and I butted heads when we first met, but we are good friends now.

Correct answer: (c) butted
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what is the meaning of butted head

[Mister Micawber]

To butt heads = to argue, to disagree.
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Native English teacher at Mister Micawber's