From WordNet (r) 3.0 (2006) [wn]:
extra
adv 1: unusually or exceptionally; "an extra fast car"
adj 1: more than is needed, desired, or required; "trying to
lose excess weight"; "found some extra change lying on
the dresser"; "yet another book on heraldry might be
thought redundant"; "skills made redundant by
technological advance"; "sleeping in the spare room";
"supernumerary ornamentation"; "it was supererogatory of
her to gloat"; "delete superfluous (or unnecessary)
words"; "extra ribs as well as other supernumerary
internal parts"; "surplus cheese distributed to the
needy" [syn: excess, extra, redundant, spare,
supererogatory, superfluous, supernumerary,
surplus]
2: added to a regular schedule; "a special holiday flight"; "put
on special buses for the big game" [syn: extra, special]
3: further or added; "called for additional troops"; "need extra
help"; "an extra pair of shoes" [syn: extra, additional]
n 1: a minor actor in crowd scenes [syn: supernumerary, {spear
carrier}, extra]
2: an additional edition of a newspaper (usually to report a
crisis)
3: something additional of the same kind; "he always carried
extras in case of an emergency" [syn: extra, duplicate]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Extra- \Ex"tra-\ [L., fr. exter. See Exterior.]
A Latin preposition, denoting beyond, outside of; -- often
used in composition as a prefix signifying outside of,
beyond, besides, or in addition to what is denoted by the
word to which it is prefixed.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Extra \Ex"tra\, a.
Beyond what is due, usual, expected, or necessary;
additional; supernumerary; also, extraordinarily good;
superior; as, extra work; extra pay. "By working extra
hours." --H. Spencer.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Extra \Ex"tra\, n.; pl. Extras.
1. Something in addition to what is due, expected, or
customary; esp., an added charge or fee, or something for
which an additional charge is made; as, at some hotels air
conditioning is an extra.
[Webster 1913 Suppl.]
2. An edition of a newspaper issued at a time other than the
regular one.
[Webster 1913 Suppl.]
3. (Cricket) A run, as from a bye, credited to the general
score but not made from a hit.
[Webster 1913 Suppl.]
4. Something of an extra quality or grade.
[Webster 1913 Suppl.]
From The Free On-line Dictionary of Computing (8 July 2008) [foldoc]:
EXTRA
Object-oriented, Pascal style, handles sets. "A Data Model
and Query Language for EXODUS", M.J. Carey et al, SIGMOD 88
Conf Proc, pp.413- 423, ACM SIGMOD Record 17:3 (Sept 1988).