SLUG

When you saw the tittle, what is the first image that come from your mind? Almost of you think slug is the creature or animal like in this picture or snail without "house". Your imagination obviously correct, but now we don't talk about it. We will talk about another slug.

Slug (Mass)
The slug is a unit of mass associated with Imperial units. It is a mass that accelerates by 1 ft/s² when a force of one pound-force (lbf) is exerted on it. Therefore a slug has a mass of 32.17405 pound-mass or 14.5939 kg.

(in terms of mass x acceleration) as

The slug is part of a subset of coherent units known as the gravitational foot-pound-second system (FPS), one of several such specialized systems of mechanical units developed in the late 19th and the 20th century. See the article poundal for an explanation of the problem such English units were introduced to solve.
The slug was first used in 1902 by Arthur Mason Worthington (1852–1916) in Dynamics of Rotation (OED), but it didn't see any significant use until decades later. A 1928 textbook says: "No name has yet been given to the unit of mass and, in fact, as we have developed the theory of dynamics no name is necessary. Whenever the mass, m, appears in our formulae, we substitute the ratio of the convenient force-acceleration pair (w/g), and measure the mass in lbs. per ft./sec.² or in grams per cm./sec.²".
Another name for this unit in early literature is the geepound.
The unit slinch (derived from the words slug-inch ) is an inch version of the slug (1 slinch = 1 lb_f·s²/in = 12 slugs).^[5] The unit blob (bl) is also an inch version of the slug (1 lb_f·s²/in).

Three approaches to mass and force units

System	Gravitational		Engineering		Absolute
Force (F)	F = m·a		F = m·a/gc = w·a/g		F = m·a
Weight (w)	w = m·g		w = m·g/gc ≈ m		w = m·g
Units	English	Metric	English	Metric	English	Metric
Acceleration (a)	ft/s2	m/s2	ft/s2	m/s2	ft/s2	m/s2
Mass (m)	slug	hyl	pound-mass	kilogram	pound	kilogram
Force (F)	pound	kilopond	pound-force	kilopond	poundal	newton

Source: wikipedia.org