The Collaborative International Dictionary of English v.0.48:
Halloo \Hal*loo"\, v. i. [imp. & p. p. Hallooed (-l[=oo]d"); p. pr. & vb. n. Hallooing.] To cry out; to exclaim with a loud voice; to call to a person, as by the word halloo. [1913 Webster] Country folks hallooed and hooted after me. --Sir P. Sidney. [1913 Webster]