A prefix meaning "out of", or informally, your former spouse
In informal English, especially US English, it is acceptable to say: ... ex (n.) is a 
casualism in the sense of a former spouse or lover ... Yours (or, for some, your's) 
is a great question, since the word ex meaning ex-girlfriend is a ... or not), and I'm 
not sure that this spelling (ex's) was necessarily done out of... [DOC] [TLE] EX       , translation and ... [PAR] Webster's New International English Dictionary; EX-  () A prefix from the latin 
preposition, ex, akin to Gr.