Definitions of fingerprint:

• noun:   biometric identification from a print made by an impression of the ridges in the skin of a finger; often used as evidence in criminal investigations
• noun:   a generic term for any identifying characteristic

  Example: "That tax bill had the senator's fingerprints all over it"

• noun:   a smudge made by a (dirty) finger
• verb:   take an impression of a person's fingerprints