Literally: beginning – spirit – vigorous – opposed
Alternately: Full of energy. Bursting with pep, vim, vigor. Lively.
Notes: This is a compound of compounds. 元気 is a very common term in Japanese, and denotes a broad theme that we might call energy, health, spirit, or wellbeing. 溌剌 is rarely found other than as part of this compound, and originally referred to a fish leaping out of the water, from which we get a metaphorical image of active vigor.
溌 may be written in its alternate form as 潑, and 剌 may be written as 溂, without any change in meaning or pronunciation. Since all of these characters fall outside of the standard set, though, hatsuratsu may also be rendered phonetically in kana as はつらつ or ハツラツ.