Con may refer to any of the following:
2. Con is also an abbreviation for confidence, in reference to a malicious manipulation of a person's trust. It may be used as a verb, as in "He conned me out of $20." It may also be used as an adjective, as in "He is a con man." As a noun, it refers to a "confidence scheme," as in, "We thought he would deliver on his promises, but the whole thing was a con." In computing, an example of a con is phishing, in which a user trusts (places confidence in) a malicious e-mail.
4. A con is any negative feedback or lack of features of a product. For example, the pros and cons of Linux vs. Windows.
5. Short for conference, con is used as an abbreviation when describing a conference or another get together. For example, DEF CON is an example of where this term is used.