Please help me understand this words' meanings.
1 Answer
バリ and ピタ are both onomatopoeia (sound effect) words - バリ represents the sound of tearing the sheet, and ピタ the "sound" of sticking it down tightly.
Onomatopoeia words are only loosely lexicalised and relatively flexible in the form they take, so they can sometimes be tricky to find in dictionaries, but you should probably be able to find バリ under バリバリ (as the reduplicated form is often treated as the most basic form for onomatopoeia) and ピタ perhaps under ピタっと (since, somewhat unusually for a sound-effect word, it isn't usually reduplicated) or as its very common variant ぴったり.