Deuterium.

(chemistry) Water containing deuterium instead of normal hydrogen (protium) (symbol D₂O); used as a moderator in nuclear reactors.

having a high centre of gravity, and liable to topple / (of an organization) having an excessive number of administrators or managers

(derogatory) Clumsy, awkward. / Excessive, overdone. / (derogatory) Lacking subtlety or nuance. / (derogatory) Overbearing, coercive; unnecessarily forceful; harsh, oppressive.

(idiomatic) sad, melancholic.

(baseball) The motion of a sharply diving sinker pitch.

(sciences, countable) Any metal that has a specific gravity greater than about 5, especially one, such as lead, that is poisonous and may be a hazard in the environment.

(idiomatic) Passionate.

(slang, archaic) A drink of strong ale and porter mixed together. / (slang, archaic) Malt liquor.

(dated) Sexual groping; erotic horseplay; foreplay.