From Middle English thikly; equivalent to thick + -ly.

• IPA: /ˈθɪkli/

thickly (comparative thicklier, superlative thickliest)

1. In a thick manner.
   • 1891, Thomas Hardy, chapter IV, in Tess of the d'Urbervilles: A Pure Woman Faithfully Presented […], volume I, London: James R[ipley] Osgood, McIlvaine and Co., […], →OCLC ↗, phase the first (The Maiden), pages 40–41 ↗:

     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 vinous bliss; all old inhabitants of the nearer end of Marlott, and frequenters of this retreat.

   • 1930, Norman Lindsay, Redheap, Sydney, N.S.W.: Ure Smith, published 1965, →OCLC ↗, page 148:

     These he held aside, ushering her into a dark sanctuary resinously scented and thickly carpeted with pine needles.

• thinly

• French: épaissement
• Russian: гу́сто