"Allegeroo" and "sis-boom-bah."

• Cheerleaders' practice
• Cheerleader's specialties
• "Go, team, go!" and others
• Screams one's head off
• "Gimme a C ...!" and "Go team!"
• Cries for help, say
• Cheerleaders' assortment
• Makes sure one is heard, maybe
• Hoots or hollers

Wiktionary Word definitions in Wiktionary
n. (plural of yell English) vb. (en-third-person singular of: yell )