Webster's Revised Unabridged Dictionary · 1913

A prefix from the Latin ultra beyond (see Ulterior), having in composition the signification beyond, on the other side, chiefly when joined with words expressing relations of place; as, ultramarine, ultramontane, ultramundane, ultratropical, etc. In other relations it has the sense of excessively, exceedingly, beyond what is common, natural, right, or proper; as, ultraconservative; ultrademocratic, ultradespotic, ultraliberal, ultraradical, etc.

Going beyond others, or beyond due limit; extreme; fanatical; uncompromising; as, an ultra reformer; ultra measures.

One who advocates extreme measures; an ultraist; an extremist; a radical. — Brougham