What is Hearsay Evidence?

Legal Definition
Testimony about out of court statements that are involving someone other than the person that is testifying. It is inadmissible because it cannot be cross examined. Civil court will use it as first hand hearsay.
Legal Definition
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, R142; 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.
-- Bouviers Law Dictionary
Legal Definition
Evidence not proceeding from the personal knowledge of the witness, but from the mere repetition of what he has heard others say. See, more fully, Hearsay.
-- Black's Law Dictionary
Legal Definition
Evidence not founded on the personal knowledge of the witness. See 43 Mont. 47, Ann. Cas. 1912C, 424, 114 Pac. 603.
-- Ballentine's Law Dictionary