To fill with love; to arouse emotionally; to inflame with intense feeling; to infuse desire into; to stir the feelings of; to excite deeply or strongly: Giving birth to her first child impassioned and animated Meg so much that she couldn't sleep at all that night.

Did you notice that the im- prefix of impassion and impassioned are intensive while the im- prefix used with the previous word (impassionate) has the meaning of “no, not, lacking,” etc.? It shows that one cannot depend on these prefixes to mean the same thing for all words.

Not too many years ago, just about every gasoline truck in the U.S. had large signs painted on them that said, INFLAMMABLE. Since most people thought that the prefix in- meant “not”, they interpreted INFLAMMABLE to mean NOT FLAMMABLE. Now the trucks carry the painted signs: FLAMMABLE to eliminate any confusion.

The Family Word Finder, a Reader‘s Digest publication, says, “Flammable has now replaced its older synonym inflammable [from Latin inflammare, to kindle) in technical and commercial usage, where the word FLAMMABLE on a dangerously combustible product is thought to serve as a more unmistakable warning.”