a prefixal use of over , prep., adv., or adj., occurring in various senses in compounds ( overboard; overcoat; overhang; overlap; overlord; overrun; overthrow ), and especially employed, with the sense of "over the limit," "to excess," "too much," "too," to form verbs, adjectives, adverbs, and nouns ( overact; overcapitalize; overcrowd; overfull; overmuch; oversupply; overweight ), and many others, mostly self-explanatory: a hyphen, which is commonly absent from old or well-established formations, is sometimes used in new coinages or in any words whose component parts it may be desirable to set off distinctly.
[ ME; OE ofer-. See OVER ]