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.
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         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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WordNet (r) 3.0 (2006):

yelled
    adj 1: in a vehement outcry; "his shouted words of encouragement
           could be heard over the crowd noises" [syn: shouted,
           yelled]