The Collaborative International Dictionary of English v.0.48:

Hearsay \Hear"say`\ (h[=e]r"s[=a]`), n.
   Report; rumor; fame; common talk; something heard from
   another.
   [1913 Webster]

         Much of the obloquy that has so long rested on the
         memory of our great national poet originated in
         frivolous hearsays of his life and conversation.
                                                  --Prof.
                                                  Wilson.
   [1913 Webster]

   Hearsay evidence (Law), that species of testimony which
      consists in a narration by one person of matters told him
      by another. It is, with a few exceptions, inadmissible as
      testimony. --Abbott.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hearsay evidence
    n 1: evidence based on what someone has told the witness and not
         of direct knowledge

Bouvier's Law Dictionary, Revised 6th Ed (1856):

HEARSAY EVIDENCE. The evidence of those who relate, not what they know
themselves, but what they have heard from others.
     2. As a general rule, hearsay evidence of a fact is not admissible. If
any fact is to be substantiated against a person, it ought to be proved in
his presence by the testimony of a witness sworn or affirmed to speak the
truth.
     3. There are, however, exceptions to the rule. 1. Hearsay is admissible
when it is introduced, not as a medium of proof in order to establish a
distinct fact, but as being in itself a part of the transaction in question,
when it is a part of the res gestae. 1 Phil. Ev. 218; 4 Wash. C. C. R. 729;
14 Serg. & Rawle, 275; 21 How. St. Tr. 535; 6 East, 193.
     4.-2. What a witness swore on a former trial, between the same
parties, and where the same point was in issue as in the second action, and
he is since dead, what he swore to is in general, evidence. 2 Show. 47; 11
John. R. 446; 2 Hen. & Munf. 193; 17 John. R. 176; But see 14 Mass. 234; 2
Russ. on Cr. 683, and the notes.
     5.-3. The dying declarations of a person who has received a mortal
injury, as to the fact itself, and the party by whom it was committed, are
good evidence under certain circumstances. Vide Declarations, and 15 John.
R. 286; 1 Phil. Ev. 215; 2 Russ. on Cr. 683.
     6.-4. In questions concerning public rights, common reputation is
admitted to be evidence.
     7.-5. The declarations of deceased persons in cases where they appear
to have been made against their interest, have been admitted.
     8.-6. Declarations in cases of birth and pedigree are also to be
received in evidence.
     9.-7. Boundaries may be proved by hearsay evidence, but, it seems, it
must amount to common tradition or repute. 6 Litt. 7; 6 Pet. 341; Cooke, R
142; 4 Dev. 342; 1 Hawks 45; 4 Hawks, 116; 4 Day, 265. See 3 Ham. 283; 3
Bouv. Inst. n. 3065, et seq. 10. There are perhaps a few more exceptions
which will be found in the books referred to below. 2 Russ. on Cr. B. 6, c.
3; Phil. Ev. ch. 7, s. 7; 1 Stark. Ev. 40; Rosc. Cr. Ev. 20; Rosc. Civ. Ev.
19 to 24; Bac. Ab. Evidence, K; Dane's Ab. Index, h.t. Vide also, Dig. 39,
3, 2, 8; Id. 22, 3, 28. see Gresl. Eq. Ev. pt. 2, c. 3, s. 3, p. 218, for
the rules in courts of equity, as to receiving hearsay evidence 20 Am. Jur.
68.