When all seniors in a high school, on a random day (typically near the end of the school year), at a predetermined time, get up and walkout of class. For high school students, this act represents a final grand act of rebellion at their school, which they despise so much. The better of walkouts work smoothly, without the interference of school authorities, include a big parade that disruptes the school, and is followed by a "skip day" the following day and/or an ingenius prank. The sweetest part of a walkout is when teachers and school authorities attempt to stop it and students walk all over them.
At 2:45 today, our grade had a walkout which went off smoothly, disrupting the school, and tomorrow is our skip day.