The Collaborative International Dictionary of English v.0.48:

ex \ex\ ([e^]ks), n.
   The letter x.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

ex \ex\ ([e^]ks), prep. (Finance)
   Without (some right); not including the right to have; as, a
   stock selling ex dividend (a stock for which the right to a
   dividend has expired the previous day); ex interest; ex
   rights.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Ex- \Ex-\ ([e^]ks).
   A prefix from the latin preposition, ex, akin to Gr. 'ex or
   'ek signifying out of, out, proceeding from. Hence, in
   composition, it signifies out of, as, in exhale, exclude;
   off, from, or out, as in exscind; beyond, as, in excess,
   exceed, excel; and sometimes has a privative sense of
   without, as in exalbuminous, exsanguinous. In some words, it
   intensifies the meaning; in others, it has little affect on
   the signification. It becomes ef- before f, as in effuse. The
   form e- occurs instead of ex- before b, d, g, l, m, n, r, and
   v, as in ebullient, emanate, enormous, etc. In words from the
   French it often appears as es-, sometimes as s- or ['e]-; as,
   escape, scape, ['e]lite. Ex-, prefixed to names implying
   office, station, condition, denotes that the person formerly
   held the office, or is out of the office or condition now;
   as, ex-president, ex-governor, ex-mayor, ex-wife, ex-convict.
   The Greek form 'ex becomes ex in English, as in exarch; 'ek
   becomes ec, as in eccentric.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

ex \ex\ ([e^]ks), n. [contraction]
   An ex-wife or ex-husband; a former spouse; -- used usually
   with a possessive; as, she invited her ex to her second
   wedding; her ex; his ex; John's ex. [informal]
   [PJC]

WordNet (r) 3.0 (2006):

ex
    adj 1: out of fashion; "a suit of rather antique appearance";
           "demode (or outmoded) attire"; "outmoded ideas" [syn:
           antique, demode, ex, old-fashioned, old-hat(p),
           outmoded, passe, passee]
    n 1: a man who was formerly a certain woman's husband [syn: ex-
         husband, ex]
    2: a woman who was formerly a particular man's wife; "all his
       exes live in Texas" [syn: ex-wife, ex]
    3: the 24th letter of the Roman alphabet [syn: X, x, ex]