The Collaborative International Dictionary of English v.0.48:

Roger \Rog"er\, n. [From a proper name Roger.]
   A black flag with white skull and crossbones, formerly used
   by pirates; -- called also Jolly Roger and pirate flag.
   [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

Jolly Roger
    n 1: a flag usually bearing a white skull and crossbones on a
         black background; indicates a pirate ship [syn: black
         flag, pirate flag, Jolly Roger, blackjack]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "Jolly Roger":
   Dannebrog, Old Glory, Star-Spangled Banner, Stars and Stripes,
   Union Flag, Union Jack, and blue, banderole, banner, banneret,
   black flag, blue ensign, bunting, burgee, coachwhip, colors,
   ensign, flag, gonfalon, gonfanon, guidon, house flag, jack,
   long pennant, merchant flag, national flag, oriflamme, pennant,
   pennon, pennoncel, red, red ensign, royal standard, signal flag,
   standard, streamer, swallowtail, tricolor, vexillum, white