IPA: /ˈbɔːrɪŋli/
KK: /ˈbɔrɪŋli/
In a way that is dull and uninteresting.
The lecture was delivered so boringly that many students fell asleep.
Boringly → It is formed from "bore" (from Old English "borian", meaning to pierce or drill) and "-ly" (a suffix meaning in a manner of). The word "boringly" means in a manner that is dull or uninteresting, as if it pierces through excitement.
Think of something that 'pierces' through interest and makes it dull — that's why 'boringly' means in a dull manner.