Bore, killjoy, party pooper, pedant. Derived from the verb занудить (to start whining, droning, or nagging), which traces back to the Proto-Slavic root *nuda (boredom, weariness, or coercion). In everyday slang, it is an exceptionally common noun used to describe a tedious, overly detailed, or humorless person who drains the energy out of a conversation by obsessing over minor rules, complaining, or lecturing others (не будь таким занудой, пойдём с нами — “don’t be such a killjoy, come with us”).
Зануда — человек, корорый всегда говорит то, с чем вы не согласны.
A bore is a person that always says that with which you do not agree.
