toxicoid

Etymology
From.

Adjective

 * 1)  Resembling a toxin but not the same.

Usage notes
Do not confuse toxicoid (a rare, dated word meaning "resembling a toxin") with (a common word meaning a weakened derivative of a toxin that is helpful because it can immunize someone against the toxin itself, whose effects are much worse). The words are etymologically related, but the meaning of more specifically as an immunizing weakened derivative is long since firmly established.