1) Arch 2) Bad 3) Disobedient 4) Elfin 5) Impish 6) Imp-like 7) Infestuous 8) Knavish 9) Naughty 10) Pixilated 11) Playful 12) Prankish 13) Puckish 14) Rude 15) Sly 16) Tricksy 1) Elfin 2) French word used in English 3) Harmful causing mischief 4) Impish 5) Implike 6) Malicious 7) Naughty 8) Pixilated 9) Playful 10) Prankish 11) Puckish 12) Rascally 13) Roguishly annoying 14) Wayward 15) Wicked 
• (a.) Causing mischief; harmful; hurtful; -- now often applied where the evil is done carelessly or in sport; as, a mischievous child.
Someone who causes trouble.
Mis'chie·vous (mĭs'che*vŭs) adjective Causing mischief; harmful; hurtful; -- now often applied where the evil is done carelessly or in sport; as, a mischievous child. 'Most mischievous foul sin.' Shak. « This false, wily, doubling disposition is intolerably ...
harmful causing mischief 
[adj] - deliberately causing harm or damage 2. [adj] - badly behaved
naughty adjective badly behaved; `he was saucy and mischievous in school`; `a naughty boy`