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

See also: unofficial

Antonym: officially

• hell-bent
• hell-for-leather
• hell-kite
• hell-rooster
• Helladic
• Helladic civilisation
• Helladic civilization
• Helladic culture
• hellbender
• hellbound
• hellcat
• hellebore
• helleborine
• Helleborus
• Helleborus foetidus
• Helleborus niger
• Helleborus orientalis
• Helleborus viridis
• Hellene
• Hellenic
• Hellenic language
• Hellenic Republic
• Hellenise
• Hellenism
• Hellenist