An oil is "essential" in the sense that it carries a distinctive scent, or essence, of the plant.

There was a distinctive unpleasant scent in the air.

Its distinctive floral scent has made neroli popular with women throughout history.

He had four soaps to choose from, all with distinctive masculine scents.

Inside, though, this is clearly a Jaguar, down to the distinctive scent of the soft leather.

That's when he'd realized that everybody had their own distinctive scent.

At once Sarah recognized his distinctive male scent in the room.

He slowed, rounded into the wind, sniffed for her distinctive scent.

Like many in this family the crushed leaves have a distinctive scent.

The distinctive scent of the pollen rushed through him.