The term tsuba (kanji: 鍔) means "sword's hand guard" in English. It is written つば in hiragana. It's pronounced roughly like "tsoo bah".
Specifically, this is the sword guard on katana and other traditional Japanese swords. Originally pronounced tsumiha, then tsumiba.
The tsuba zeriai (鍔迫り合い, つばぜりあい) is a move in kendo where the bamboo swords are locked against each other. Colloquially, the phrase can describe any fierce competition in sports.