To disregard/abandon/ditch a person or other entity. The word is actually an acronym for "a man for his own".
Origins of the term:
"Amfho" which came about one sweltering afternoon in Kuala Lumpur, Malaysia.
A Muslim dude (a bit wasted at the end of a hot day in the holy Muslim month of Ramadhan, while he was fasting) was responding to his Christian friend who offered to fast with him as a show of support. He replied "nah don't worry about it, a man for his own" (where he had inavertently spliced together "every man for himself" and "unto each his own", and mutated the first word).
The term amfho subsequently achieved a great deal of popularity in Sunway College, and it has now been exported to the rest of the world, most notably Australia.
"We amfho'd him as he was running late, again."
"British forces were getting whipped by the Japanese army, so they just decided "amfho" and left the region."
"That bitch amfho's guys the moment they run into financial trouble."