What is the meaning of taut?

It's an adjective which means tightly stretched or tense. Taut's synonym is tight.

You can use word taut when talking about tense, not relaxed muscles.

Or streched fabric.

Taut could mean several things, all with the general same meaning.

Example 1: (Meaning) Tight, tense, stretched, rigid.

Example 2: "The rope was pulled taut, stretched across the two trees, safe for walking across."

Example 3: "The man's muscles were taut, he looked tense and ready to run at any moment."