Source : Webster's Revised Unabridged Dictionary (1913)

Reticent \Ret"i*cent\, a. [L. reticens, p. pr. of reticere to
   keep silence; re- + tacere to be silent. See {Tacit}.]
   Inclined to keep silent; reserved; uncommunicative.

Source : WordNet®

reticent
     adj 1: temperamentally disinclined to talk [syn: {untalkative}]
     2: cool and formal in manner [syn: {reserved}, {restrained}, {unemotional}]
     3: reluctant to draw attention to yourself [syn: {self-effacing}]