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Webster 1913 Edition

(r?-kw?r′?-b’l)

Adj.

Capable of being required; proper to be required.

Sir M. Hale.

Adj.

[from require.] That may be required; fit or proper to be demanded.

requirable ‎(not comparable)

Capable of being required.
Proof of citizenship is requirable for some services but not for all.