Definitions

1. noun

A dark nebula in the constellation Orion, seen as a silhouette against the more luminous background of interstellar gas and dust.

“The astronomer pointed out the beautiful horsehead nebula in the night sky.”

2. proper noun

A part of the Orion Nebula, also known as Barnard 33, an interstellar cloud.

“The horsehead is an iconic feature in the Orion Nebula.”