Auto correlation is the correlation of one signal with itself.

Cross correlation is the correlation of one signal with a different signal.

positive correlation

Faunal Cross-correlation is the use of animal bones found within an archaeological site to determine a relative date.

correlation is a technique of correlating two signals with each other and producing the third signal. In correlation if two different signals are used it is called cross correlation and if same signal is correlated with itself it is called as auto correlation.

Anant Suryakant Trivedi has written:

'A non-contacting ultrasonic cross correlation flowmeter for liquids'