1. Without formality
   "he visited us informally" 
2. With the use of colloquial expressions
   - colloquially, conversationally

See also: informal

Antonym: formally

• enemy
• energetic
• energetically
• energetics
• energid
• energise
• energiser
• energising
• energize
• energizer
• energizing
• energy
• Energy Department
• energy level
• energy of activation
• Energy Secretary
• energy state
• energy unit
• energy-absorbing
• energy-releasing
• energy-storing
• enervate
• enervated
• enervating
• enervation