That depends on what your definition of “in-” is

According to M-W’s word of the day for Oct 7th:

inflammable \in-FLAM-uh-bul\ adjective

*1 : flammable
2 : easily inflamed, excited, or angered : irascible

Example sentence:
The U.S. Commerce Department adopted rules banning inflammable children’s sleepwear in the 1970s.

Did you know?
“Combustible” and “incombustible” are opposites but “flammable” and “inflammable” are synonyms. Why? The “in-” of “incombustible” is a common prefix meaning “not,” but the “in-” of “inflammable” is a different prefix. “Inflammable,” which dates back to 1605, descends from the Latin “inflammare” (“to inflame”), from “in-” (here meaning “in” or “into”) plus “flammare” (“to flame”). “Flammable” also comes from “flammare,” but didn’t enter English until 1813. In the early 20th century, firefighters worried that people might think “inflammable” meant “not able to catch fire,” so they adopted “flammable” and “nonflammable” as official safety labels and encouraged their use to prevent confusion. In general use, “flammable” is now the preferred term for describing things that can catch fire, but “inflammable” is still occasionally used with that meaning as well.

*Indicates the sense illustrated in the example sentence.

This has to stop. Now. Every time I hear “inflammable” I have to pause and think about it for a second. Somebody do something!