Real Dictionary

hyper
If someone is hyper, they are very excited and energetic.

hyper in American English
high-strung; keyed up

hyper in American English 1
adjective: overexcited; overstimulated; keyed up
noun: a person who is hyper

hyper in American English 2
noun: a person who promotes or publicizes events, people, etc., esp. one who uses flamboyant or questionable methods; promoter; publicist

hyper in British English
adjective: overactive; overexcited

hyper-
prefix: Hyper- is used to form adjectives that describe someone as having a lot or too much of a particular quality.

hyper- in American English
over, above, more than the normal, excessive
prefix: a prefix appearing in loanwords from Greek, where it meant “over,” usually implying excess or exaggeration (hyperbole). On this model, hyper- is used, especially as opposed to hypo-, in the formation of compound words (hyperthyroid)

hyper- in British English
prefix: above, over, or in excess