a person who has not reached a definite opinion on a subject, esp as a response to a questionnaire
don't-know in American English
(ˈdountˈnou)
noun
a person who has no opinion or is undecided, as in answering an item on a public-opinion poll
Word origin
[1885–90]This word is first recorded in the period 1885–90. Other words that entered Englishat around the same time include: classified, roller coaster, scrum, seminar, toner