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Webster 1913 Edition

Adj.

Not constant; inconstant; fickle; changeable.

[Obs.]

Shak.

–

Un-con′stant-ly

adv.

[Obs.]

–

Un-con′stant-ness

Noun.

[Obs.]

Adj.

Not constant; not steady or faithful; fickle; changeable. [Inconstant is now used.]

unconstant ‎(comparative more unconstant, superlative most unconstant)

inconstant
- 1826, Mary Shelley, The Last Man:
  Within, was the peace as of innocence, reckless blindless, deluding joy, hope, whose still anchor rested on placid but unconstant water.