1. a person or thing that breaks through or makes a breach in something
Usage: often used in military or tactical contexts
2. a person or entity that violates or breaks an agreement, law, or obligation
Usage: legal or formal context
3. a whale or other marine animal that breaches, leaping out of the water
Usage: zoological context

Examples

• The breacher used explosives to open a path through the wall.
• The contract breacher was held liable for damages.
• We watched a breacher—a humpback whale—leap dramatically from the ocean.
• Military breachers are trained to penetrate fortified positions.
• The breacher of the agreement faced legal consequences.
• The whale was a spectacular breacher, jumping clear of the water multiple times.