Disappoint, v. t. [imp. & p. p. Disapointed; p. pr. & vb. n. Disappointing.] — Webster enters it under “disappoint”
Etymology: [OF. desapointier, F. désappointer; pref. des- (L. dis-) + apointier, F. appointier, to appoint. See Appoint.]
1. To defeat of expectation or hope; to hinder from the attainment of that which was excepted, hoped, or desired; to balk; as, a man is disappointed of his hopes or expectations, or his hopes, desires, intentions, expectations, or plans are disappointed; a bad season disappoints the farmer of his crops; a defeat disappoints an enemy of his spoil. I was disappointed, but very agreeably. Macaulay.
Note: Disappointed of a thing not obtained; disappointed in a thing obtained.
2. To frustrate; to fail; to hinder of result. His retiring foe Shrinks from the wound, and disappoints the blow. Addison.
Syn. -- To tantalize; fail; frustrate; balk; baffle; delude; foil; defeat. See Tantalize.
Shades of meaning
Fernald lists disappointing only as an antonym, under delightful.
He lists it without comment; the entries above explain its neighbors.