To Feel Nervous
To Get Tense
する verb
緊張 means "nervousness" or "tension." So, the verb version is to feel nervous or to get tense.
People often use 緊張する when they're about to do something important, like giving a speech or taking a test. In formal contexts it can also be used to talk about muscles physically getting tense.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
試合前に緊張するのはよくあることです。
It's common to get nervous before a match.
初めてのデートで緊張した。
I was nervous on my first date.
緊張しすぎて、手がふるえました。
I was so nervous that my hands started shaking.
大事なプレゼンなので、とても緊張しています。
I'm very nervous for an important presentation.