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Webster 1913 Edition

adv.

In a pert manner.

adv.

Briskly; smartly; with prompt boldness.

Saucily; with indecorous confidence or boldness.

pertly ‎(comparative more pertly, superlative most pertly)

In a manner that is lively or high-spirited
- 1922, Sinclair Lewis, “24”, in Babbitt:
  "Dearie, you aren't going to go and get peevish, are you?" She spoke pertly. He wanted to spank her.