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

See also: unofficial

Antonym: officially

• piccalilli
• piccaninny
• piccolo
• pice
• Picea
• Picea abies
• Picea breweriana
• Picea engelmannii
• Picea glauca
• Picea mariana
• Picea obovata
• Picea orientalis
• Picea pungens
• Picea rubens
• Picea sitchensis
• piceous
• pichi
• pichiciago
• pichiciego
• Picidae
• piciform bird
• Piciformes
• pick
• pick and choose
• pick apart