The Collaborative International Dictionary of English v.0.48:

Yell \Yell\, n.
   A sharp, loud, hideous outcry.
   [1913 Webster]

         Their hideous yells
         Rend the dark welkin.                    --J. Philips.
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The Collaborative International Dictionary of English v.0.48:

Yell \Yell\ (y[e^]l), v. i. [imp. & p. p. Yelled; p. pr. & vb.
   n. Yelling.] [OE. yellen, [yogh]ellen, AS. giellan, gillan,
   gyllan; akin to D. gillen, OHG. gellan, G. gellen, Icel.
   gjalla, Sw. g[aum]lla to ring, resound, and to AS., OS., &
   OHG. galan to sing, Icel. gala. Cf. 1st Gale, and
   Nightingale.]
   To cry out, or shriek, with a hideous noise; to cry or scream
   as with agony or horror.
   [1913 Webster]

         They yelleden as feendes doon in helle.  --Chaucer.
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         Nor the night raven, that still deadly yells.
                                                  --Spenser.
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         Infernal ghosts and hellish furies round
         Environed thee; some howled, some yelled. --Milton.
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The Collaborative International Dictionary of English v.0.48:

Yell \Yell\, v. t.
   To utter or declare with a yell; to proclaim in a loud tone.
   --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

yell
    n 1: a loud utterance; often in protest or opposition; "the
         speaker was interrupted by loud cries from the rear of the
         audience" [syn: cry, outcry, call, yell, shout,
         vociferation]
    2: a loud utterance of emotion (especially when inarticulate);
       "a cry of rage"; "a yell of pain" [syn: cry, yell]
    v 1: utter a sudden loud cry; "she cried with pain when the
         doctor inserted the needle"; "I yelled to her from the
         window but she couldn't hear me" [syn: shout, shout
         out, cry, call, yell, scream, holler, hollo,
         squall]
    2: utter or declare in a very loud voice; "You don't have to
       yell--I can hear you just fine" [syn: yell, scream]