The word is normally used in the phrase
to run amok/amuck, meaning 'to run about wildly in a violent rage', and is an extension of a particular meaning in Malay anthropology
(Edward now wore the manic look of some animal transferred into the wrong environment, as though he might run amok, or bite—Penelope Lively, 1990).
It also has figurative uses not involving physical action
(With Thatcher running amok through the welfare state, lobby groups are preoccupied defending what was once thought unassailable—New Scientist, 1991
It wasn't his fault that her feelings seemed to be running amok—E. Rees, 1992).
Occasional unidiomatic uses occur
(The place was amok with running kids with running noses—weblog, British English 2005 [Old English (up to 1150)C]).
The spelling
amok, which is closer to the original Malay
amoq meaning 'attacking in frenzy', is more common (five times more in the Old English (up to 1150)C) and is preferable.