(organic chemistry) Hypothetically, one of the Platonic hydrocarbons, C₄H₄, having the carbon atoms at the vertices of a tetrahedron; has not yet been synthesized, and would be very unstable.

(logic) An argument whose conclusion is supported by two premises, of which one contains the term that is the predicate of the conclusion, and the other contains the term that is the subject of the...

(poetic) Full of mystery; mysterious.

plural of Axtell