The Collaborative International Dictionary of English v.0.48:

Ribald \Rib"ald\, a.
   Low; base; mean; filthy; obscene.
   [1913 Webster]

         The busy day,
         Waked by the lark, hath roused the ribald crows.
                                                  --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ribald \Rib"ald\, n. [OE. ribald, ribaud, F. ribaud, OF. ribald,
   ribault, LL. ribaldus, of German origin; cf. OHG hr[imac]pa
   prostitute. For the ending -ald cf. E. Herald.]
   A low, vulgar, brutal, foul-mouthed wretch; a lewd fellow.
   --Spenser. Pope.
   [1913 Webster]

         Ribald was almost a class name in the feudal system . .
         . He was his patron's parasite, bulldog, and tool . . .
         It is not to be wondered at that the word rapidly
         became a synonym for everything ruffianly and brutal.
                                                  --Earle.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ribald
    adj 1: humorously vulgar; "bawdy songs"; "off-color jokes";
           "ribald language" [syn: bawdy, off-color, ribald]
    n 1: a ribald person; someone who uses vulgar and offensive
         language