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Webster 1913 Edition

adv.

In a lavish manner.

adv.

With profuse expense; prodigally; wastefully.

lavishly ‎(comparative more lavishly, superlative most lavishly)

In a lavish manner, expending profusely.
He was noted to entertain lavishly, throwing the biggest and best parties in town.‎
- 1893, Walter Besant, The Ivory Gate, chapter II:
  At twilight in the summer […] the mice come out. They […] eat the luncheon crumbs. Mr. Checkley, for instance, always brought his dinner in a paper parcel in his coat-tail pocket, and ate it when so disposed, sprinkling crumbs lavishly—the only lavishment of which he was ever guilty—on the floor.

in a lavish manner