rat-tail

noun

• 1 (also rat's tail) a narrow hairless tail like that of a rat, or something that resembles one: [as modifier]:he’s growing it longer, with a thin rat-tail braid at the back
• (rat's tails) British informal hair hanging in lank, damp or greasy strands.

• 2a fish with a long, thin tail, in particular:
• another term for grenadier (sense 2).
• another term for rabbitfish (sense 1).