1. The first beat of a measure of music. Refers to the downward motion displayed by a conductor on beat one.
2. In the music industry, the time when a recording session or live show is scheduled to begin. Everything must be set up and ready to go before this time. Often ignored by big stars with bigger egos.
An abbreviation of "download this content and learn it". Where students are directed to teach themselves using material supplied on a web page as videos, written documents or PDFs.