Merriam-Webster's Collegiate® Dictionary, 11th Edition
YELL
I. verb
Etymology: Middle English, from Old English giellan; akin to Old High German gellan to yell, Old English galan to sing Date: before 12th century intransitive verb to utter a loud cry, scream, or shout, to give a cheer usually in unison, transitive verb to utter or declare with or as if with a yell ; shout , yeller noun
II. noun
Date: 14th century
scream , shout , a usually rhythmic cheer used especially in schools or colleges to encourage athletic teams