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Webster 1828 Edition

adv.

Attentively; carefully; cautiously. Listen heedfully to good advice.

Watchfully.

heedfully ‎(comparative more heedfully, superlative most heedfully)

In a heedful manner.
- 1603, John Florio, translating Michel de Montaigne, Essayes, London: Edward Blount, OCLC 946730821, II.8:
  they did, as long as they were possessed with that care, heedefully abstaine from all venerian acts, and touching of women.