1) Closelipped 2) Close mouthed 3) Deadpan 4) Distant 5) Expressionless 6) Guarded 7) Inarticulate 8) Incommunicado 9) Incommunicative 10) Inexpressive 11) Mum 12) Noncommittal 13) Reserved 14) Reticent 15) Secretive 16) Taciturn 17) Tightlipped 18) Unarticulate 19) Unexpressive 20) Unrevealing 
[adj] - not inclined to talk or give information or express opinions
uncommunicative 1. Not inclined to talk or to give information or to express opinions. 2. Tending not to talk nor to disclose information; reserved; taciturn.
adjective not inclined to talk or give information or express opinions
not inclined to talk or disclose information; reserved; taciturn.
[SAT terms] not inclined to talk or give information or express opinions