Recognised medical condition arising from a period of prolonged cohabitation with a recently exed spouse or domestic partner, whereby hitherto amicable separations risk lurching into loathing and recriminations due to sudden lack of shared interests and/or future aspirations, see also ex stress.

A word Harry Styles uses to explain you.

When you have a friend called Amy (or any name similiar to that) and she has a weird humor noone understands but you suddenly understand it and maybe using it on a daily basis, you have a rare disease called Amicism. Careful it is very contagious!!

A girl who is very nice but kind of weird.

She likes giving rusty trombones and being a mediocre holy paladin.