exit poll

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A poll taken of a sample of voters as they leave a polling place, used especially to predict the outcome of an election or determine the voters' opinions and characteristics.

from the GNU version of the Collaborative International Dictionary of English.

• a survey poll taken by interviewing voters as they leave (exit) the polling place, to determine how they voted and for what reasons; -- it is usually taken by news media to learn at an early time (often before the balloting has finished) who the winners are, and sometimes the reasons for the voters' choices.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A poll taken of a sample of voters as they leave a voting station; used to predict the outcome of an election.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a poll of voters as they leave the voting place; usually taken by news media in order to predict the outcome of an election