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Webster 1913 Edition

adv.

In a thick manner; deeply; closely.

adv.

Deeply; to great depth.

Closely; compactly.

In quick succession.

thickly ‎(comparative thicklier or more thickly, superlative thickliest or most thickly)

In a thick manner.
- 1891, Thomas Hardy, Tess of the d’Urbervilles , chapter IV
  In a large bedroom upstairs, the window of which was thickly curtained with a great woollen shawl lately discarded by the landlady, Mrs Rolliver, were gathered on this evening nearly a dozen persons, all seeking beatitude; all old inhabitants of the nearer end of Marlott, and frequenters of this retreat.

in a thick manner