Using your own product in real, daily work so the team feels every bug, missing feature, and bad default before customers do, also called eating your own dog food.
The phrase entered software through Microsoft, where manager Paul Maritz emailed a colleague in 1988 with the subject 'Eating our own Dogfood,' asking that internal teams move to the company's own tools. The idea spread through Windows and Office, and the term has been the industry shorthand for self-use ever since.