Man-in-the-middle attack
An attack where a user gets between the sender and receiver of information and sniffs any information being sent. In some cases, users may be sending unencrypted data, which means the man-in-the-middle (MITM) can easily obtain any unencrypted information. In other cases, a user may be able to obtain the information from the attack but have to unencrypt the information before it can be read.
Also see: Encrypt, Security definitions