Definition
To correctly or incorrectly guess which side of a coin will face upwards after being tossed and landing.
Before the start of the soccer match, the captains will toss a coin, and the team that wins the toss gets to choose to kick-off or which side to play on.
We tossed a coin to decide, and I lost the toss, so you get to go first.
In tennis, the right to serve first is often decided by a coin toss; the person who wins the toss gets to choose whether to serve first.