Slug

Slug

1. A unit of mass; the mass of a free body which if acted upon by a force of 1 pound would experience an acceleration of 1 foot per square second; thus approximately 32.16 pounds.
2. A terrestrial or marine gastropod mollusk with a soft, undeveloped shell or no shell at all. See Sea Slug
3. A large, solid metal projectile.

References

This article is based on NASA's Dictionary of Technical Terms for Aerospace Use