As verbs the difference between drilling and countersinking
is that drilling is present participle of lang=en while countersinking is present participle of lang=en.
As a noun drilling
is act of drilling.
drilling
English
Etymology 1
Verb
(head)
Noun
(
en noun)
Act of ing.
A heavy, twilled fabric of linen or cotton; drill.
Etymology 2
From German drei (three)
Noun
(
en noun)
A long firearm with three (or rarely, four) barrels.