'Re-' definitions:

Definition of 'Re-'

From: GCIDE

Re- \Re-\ (r[=e]-). [L. re-, older form (retained before vowels) red-: cf. F. re-, r['e]-.] A prefix signifying back, against, again, anew; as, recline, to lean back; recall, to call back; recede; remove; reclaim, to call out against; repugn, to fight against; recognition, a knowing again; rejoin, to join again; reiterate; reassure. Combinations containing the prefix re- are readily formed, and are for the most part of obvious signification. [1913 Webster]
Note: With the increase of electronic connunications, in which the vowels with a diaeresis (e.g. ["e]) are seldom used in contrast with printed materials, some words with re followed by a vowel are now spelled with a hyphen to indicate that the two vowels are to be pronounced as two syllables rather than as one syllable, as in re-emerge rather than re["e]merge. The unbroken forms (e.g. reemerge) are, however, usually more commonly used, and the pronunciation with two syllables for the two vowels is taken as understood. [PJC]