to fear: to hold a standing dread of someone powerful, and (of a thing) to be dreadful to look at
Daniel is the only book that uses this word, and it is that book's plain word for being afraid. Whole populations live in fear of Nebuchadnezzar, whose word can kill or spare at will. Later a Persian king writes a decree telling everyone in his realm to fear the God of Daniel instead. In both places the fear is a settled posture toward someone who holds power over you, not a passing shudder.
The same word also turns around to describe the thing that is feared. The towering statue in Nebuchadnezzar's dream and the fourth beast in Daniel's night vision are not afraid of anything; they are frightening to look at, terrible in their very appearance. English needs two words for this, "afraid" for the person and "dreadful" for the thing, while Aramaic uses one word for both.
One use pushes further still. In Daniel 4:5 the dream itself does the frightening, and the king says it made him afraid, while a second word in the same breath (בְּהַל) says the visions alarmed him. The pairing shows the difference between them: this word is the steady dread of something fearsome, and the other is the sudden jolt of panic.
It keeps company with other fear words. Twice it stands right beside the verb for trembling (זוּעַ), so that shaking and fear are named together, and once a rare word for "terrifying" (אֵימְתָן) is stacked on top of it to make the fourth beast worse still.