1. In an unnecessary manner
   "they were unnecessarily rude" 
2. Without any necessity
   "this marathon would exhaust him unnecessarily"

See also: unnecessary

Antonym: necessarily

• of course
• of each person
• of import
• of late
• of necessity
• of sorts
• of sound mind
• of the essence
• of unsound mind
• ofay
• off
• off her guard
• off his guard
• off one's guard
• off spin
• off the beaten track
• off the cuff
• off the hook
• off the record
• off year
• off your guard
• off-and-on
• off-axis reflector
• off-base
• off-Broadway