IPA: /ˈspɛkjʊləli/
KK: /ˈspɛkjələrli/
In a way that reflects light like a mirror, producing a clear image or reflection.
The surface of the lake was specularly smooth, reflecting the sky perfectly.
Specularly → It is formed from "specula" (from Latin, meaning mirror or to look) and the suffix "-ly" (meaning in a manner). The word "specularly" refers to something done in a manner that reflects or resembles a mirror.
Think of 'specula' meaning mirror, and remember that 'specularly' describes something that is done in a reflective manner.