Apologies up front for the unseemly delay in the reply. :) Not
ignoring you, just been overloaded at work _&_ home; every cotton-
pickin' thing from working up a web page to fixing a lawn sprinkler
system once & a washing machine 3 times. Don't ask; trust me, you
don't want to know. 
MG> MG> oher than his or her spouse: ADULTEROUS".
MG> BN> I just love it when I get to be like Gunny Foley in "An Officer
MG> BN> & a Gentleman." 
MG> Sorry, that reference is lost on me due to the passage of time.
MG> The black drill instructor?
Yup, that's him, all right.  The one who said (semi-quote) "In
every class, there's always one person who thinks he's smarter
than me." 
MG> BN> word.  Of course if one *prefers* to limit to abridged tools, I
MG> BN> suppose one could claim there was only one definition.
MG> BN> 
MG> "Extramarital" isn't in my first edition (unabridged) OED or the
MG> 1933 supplement.  Lots of "extra-" words and an explanation of
MG> the prefix to mean "outside of", but that's about it.
True; back then they put a fair amount of stock in users doing some
of their own etymological construction & didn't spell out much of
what was generally considered obvious, & since most everyone used
the same frame of reference it didn't matter all that much. Then
Americans got into the act & things sort of went downhill from
there.   The Shorter OED (1936 vintage) defines the prefix
as meaning "situated outside of something" & "lying outside the
province or scope of."  (It then refers as an example specifically
to "extramatrimonial," BTW.)  The Thorndike Barnhart Student's
Dictionary (forget the year, but fairly recent, 17 years or so IIRC)
defines extramarital as "having to do with sexual relations outside
of marriage."  So both of those do pretty much clearly include both
the married & non-married states. 
In any event (since this is wayyyyy off-topic at this point )
it all boils pretty much down to whether or not the individual wants
to focus narrowly or more all-inclusive (i.e., the more recent as
opposed to more historical senses of the word.) 
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