Asperity, n.; pl. Asperities.
Etymology: [L. asperitas, fr. asper rough: cf. F. aspérité.]
1. Roughness of surface; unevenness; -- opposed to smoothness. "The asperities of dry bodies." Boyle.
2. Roughness or harshness of sound; that quality which grates upon the ear; raucity.
3. Roughness to the taste; sourness; tartness.
4. Moral roughness; roughness of manner; severity; crabbedness; harshness; -- opposed to mildness. "Asperity of character." Landor. It is no very cynical asperity not to confess obligations where no benefit has been received. Johnson.
2 more senses
5. Sharpness; disagreeableness; difficulty. The acclivities and asperities of duty. Barrow.
Syn. -- Acrimony; moroseness; crabbedness; harshness; sourness; tartness. See Acrimony.
Shades of meaning
Fernald has no entry of its own for asperity; he lists it under acrimony.
Where he writes about it:
Acerbity is a sharpness, with a touch of bitterness, which may arise from momentary annoyance or habitual impatience; asperity is keener and more pronounced, denoting distinct irritation or vexation; in speech asperity is often manifested by the tone of voice rather than by the words that are spoken. — from acrimony
One might speak with momentary asperity to his child, but not with acrimony, unless estrangement had begun. — from acrimony