hearsay

Short definition from Wiktionary

Noun

1. 1
   Information that was heard by one person about another that cannot be adequately substantiated.
2. 2
   Evidence based on the reports of others, which is normally inadmissible because it was not made under oath, rather than on personal knowledge.
3. 3
   An out-of-court statement offered in court to prove the truth of the matter asserted (or the in-court testimony which recites such a statement), which is normally inadmissible (because it is not subject to cross-examination) unless it falls under one of a number of exceptions.