noun
gagging; silencing; hush money; tiny morsel
Literally 'mouth-blocking'. Can refer to physically preventing someone from speaking, figuratively silencing them (e.g., with a bribe), or a morsel so small it barely fills the mouth. The 'tiny morsel' sense is rare and often appears in set phrases like 口塞ぎにもならない (not even enough to stop one's mouth).
彼は証人の口塞ぎに金を渡した。
He gave money to the witness as hush money.
こんな小さなケーキでは口塞ぎにもならない。
A cake this small is hardly a mouthful.