1. Not knowledgeable about something specified
   "a person unacquainted with our customs"
   - innocent 
2. Having little or no knowledge of
   "unacquainted with city ways"
   - unacquainted with, unfamiliar with

See also: unfamiliar, uninformed

• upper-class
• upper-level
• upper-lower-class
• upper-middle-class
• Upper-Normandy
• uppercase
• uppercut
• uppermost
• uppish
• uppishly
• uppishness
• uppity
• uppityness
• UPPP
• Uppsala
• upraise
• upraised
• uprate
• uprear
• upright
• upright piano
• uprightly
• uprightness
• uprise
• uprising