IPA: /ˈlækrɪˌmeɪtə/
KK: /ˈlækrɪˌmeɪtər/
A substance that causes tears to be produced, often used in crowd control or self-defense.
The police used a lachrymator to disperse the protesters.
Lachrymator is formed from "lachryma" (from Latin, meaning tear) and "-ator" (a suffix indicating an agent or something that causes). The word refers to a substance that causes tears or induces crying.
Think of 'lachryma' meaning tear, and remember that a 'lachrymator' is something that causes tears.
No commonly confused words.