uncommunicative (adj.)

• aloof
• autistic
• bashful
• canny
• careful
• cautious
• circumspect
• close
• closemouthed
• dark
• deliberate
• discreet
• dissociable
• distant
• evasive
• gingerly
• guarded
• heedful
• hesitant
• incompatible
• judicious
• meaningless
• mindful
• morose
• noncommittal
• nongregarious
• offish
• pawky
• politic
• prudent
• regardful
• reserved
• reticent
• safe
• secret
• secretive
• self-contained
• self-sufficient
• shifty
• snug
• standoffish
• sullen
• taciturn
• tentative
• thorough
• unadventurous
• unapproachable
• unbending
• uncongenial
• unenterprising
• unfriendly
• unsociable
• unsocial
• withdrawn