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Webster 1913 Edition

Adj.

Of or pertaining to billows; swelling or swollen into large waves; full of billows or surges; resembling billows.

And whitening down the many-tinctured stream,
Descends the

billowy

foam.

Thomson.

Adj.

Swelling, or swelled into large waves; wavy; full of billows, or surges.

billowy ‎(comparative billowier, superlative billowiest)

Of or pertaining to billows; swelling or swollen into large waves; full of billows or surges; resembling billows.
- 1919, W. Somerset Maugham, The Moon and Sixpence, chapter 58
  [...] Tiare clasped me to her vast bosom, so that I seemed to sink into a billowy sea, and pressed her red lips to mine.

full of billows or surges