1. Without official authorization
   - on the side 
2. Not in an official capacity
   "unofficially, he serves as the treasurer"

See also: unofficial

Antonym: officially

• poenology
• Poephila
• Poephila castanotis
• poesy
• poet
• poet laureate
• poet-singer
• poetaster
• poetess
• poetic
• poetic justice
• poetic licence
• poetic license
• poetic rhythm
• poetical
• poetically
• poetics
• poetise
• poetiser
• poetize
• poetizer
• poetry
• pogey
• pogge
• pogo