(noun) the 6th letter of the Greek alphabet
Source: WordNet® 3.1
zeta (plural zetas)
The sixth letter of the modern Greek alphabet (Ζ, ζ) preceded by epsilon (Ε, ε) and followed by eta, (Η, η); or the seventh letter in the ancient Greek alphabet, in which it is preceded by digamma (Ϝ, ϝ)
(mathematics) A mathematical function formally known as the Riemann zeta function.
(physics) Acronym of zero-energy thermonuclear assembly/apparatus (a torus-shaped reactor used in the mid-20th century to carry out experiments in plasma physics and temperature-controlled thermonuclear reactions)
A medieval state roughly equivalent to modern Montenegro.
Zeta (plural Zetas)
A member of Los Zetas, a Mexican criminal syndicate.
Ze"ta, n. Etym: [L., from Gr. Zed.]
Definition: A Greek letter [z] corresponding to our z.
Source: Webster’s Unabridged Dictionary 1913 Edition