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

See also: unofficial

Antonym: officially

• liturgically
• liturgics
• liturgiology
• liturgist
• liturgy
• liv
• livable
• live
• live axle
• live birth
• live body
• live down
• live in
• relative-in-law
• relatively
• relativise
• relativism
• relativistic
• relativistic mass
• relativistically
• relativity
• relativity theory
• relativize
• relator
• relatum