hackathon n. 1. An event typically lasting several days in which a large number of people meet to engage in collaborative computer programming (also known as a hackfest or codefest). 2. An event where computer programmers get together to work intensely on software projects (also known as a hack day).
BS Definition: An event that computer programmers typically travel to attend (and have to adjust to the light of being outside for the first time in years as a result).
Origin: What linguists would call a “portmanteau” (meaning “a blending”),