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Webster 1913 Edition

Verb.

[1st pref.

un-

bolt

To remove a bolt from; to unfasten; to unbar; to open.

“He shall unbolt the gates.”

Shak.

Verb.

To explain or unfold a matter; to make a revelation.

[Obs.]

“I will unbolt to you.”

Shak.

Verb.

To remove a bolt from; to unfasten; to open; as, to unbolt a gate.

unbolt ‎(third-person singular simple present unbolts, present participle unbolting, simple past and past participle unbolted)

(transitive) To unlock by undoing the bolts of.
- Shakespeare
  He shall unbolt the gates.

unlock by undoing bolts