Tact, n.
Etymology: [L. tactus a touching, touch, fr. tangere, tactum, to touch: cf. F. tact. See Tangent.]
1. The sense of touch; feeling. Did you suppose that I could not make myself sensible to tact as well as sight Southey. Now, sight is a very refined tact. J. Le Conte.
2. (Mus.)
The stroke in beating time.
3. Sensitive mental touch; peculiar skill or faculty; nice perception or discernment; ready power of appreciating and doing what is required by circumstances. He had formed plans not inferior in grandeur and boldness to those of Richelieu, and had carried them into effect with a tact and wariness worthy of Mazarin. Macaulay. A tact which surpassed the tact of her sex as much as the tact of her sex surpassed the tact of ours. Macaulay.
Shades of meaning
Fernald has no entry of its own for tact; he lists it under address.
Where he writes about it:
It includes adroitness and discretion to know what to do or say and what to avoid; ingenuity to devise; readiness to speak or act; the dexterity that comes of practise; and tact, which is the power of fine touch as applied to human character and feeling. — from address