Glossary
Swing
In one line: A decisive, fast peek towards an enemy who is probably waiting, to take the fight right away.
What it means
A swing is an aggressive peek: you do not sneak a look, you commit to the fight. You use it when you want a duel you know is there, for example right after a flash or when you hear the enemy reloading or distracted.
The difference from a normal peek is intent: a swing looks for the kill now. It is strong when the enemy is in trouble and dangerous when they are waiting with their crosshair ready.
An example
Your teammate tags a defender who ducks back on low health. You swing the same angle immediately: they are low and repositioning, and you catch them before they settle.