Longman Dictionary of Contemporary English
intra-
prefix
EXAMPLES FROM OTHER ENTRIES
▪ an intranet
The Collaborative International Dictionary
Intra-
Intra- \In"tra-\ [L. intra, prep., within, on the inside; akin to inter. See Inter-.] A prefix signifying in, within, interior; as, intraocular, within the eyeball; intramarginal.
Douglas Harper's Etymology Dictionary
intra-
word-forming element meaning "within, inside, on the inside," from Latin intra "on the inside, within," related to inter "between," from PIE *en-t(e)ro-, from root *en "in" (see in). Commonly opposed to extra-, but the use of intra as a prefix was rare in classical Latin.
Wiktionary
intra-
pre. (non-gloss: a prefix signifying inside, within, interior, during)