The Collaborative International Dictionary of English v.0.48:
Questioner \Ques"tion*er\, n. One who asks questions; an inquirer. "Little time for idle questioners." --Tennyson. [1913 Webster]WordNet (r) 3.0 (2006):
questioner n 1: someone who asks a question [syn: inquirer, enquirer, questioner, querier, asker]