Dictionary.net

• dun-dr[=e]r'i, adj. like Lord Dundreary--in Sothern's creation of the part, a lisping and brainless dandy, wearing long side-whiskers.

1908 - Chambers's Twentieth Century Dictionary of the English Language
By Thomas Davidson

• D. whiskers, long side whiskers worn without beard.

1919 - The concise Oxford dictionary of current English
By Sir Augustus Henry