microdot

From micro- + dot.

microdot (plural microdots)

1. A text or photographic image that has been reduced in size to that of a typographical dot in order to escape detection by unintended recipients.
2. (informal) A small tablet containing lysergic acid diethylamide (LSD).

microdot (third-person singular simple present microdots, present participle microdotting, simple past and past participle microdotted)

1. (transitive) To mark with a microdot.
2. (transitive) To make into a microdot.