Reticent, a.
Etymology: [L. reticens, p. pr. of reticere to keep silence; re- + tacere to be silent. See Tacit.]
Inclined to keep silent; reserved; uncommunicative.
Shades of meaning
Fernald has no entry of its own for reticent; he lists it under taciturn.
He lists it without comment; the entries above explain its neighbors.