Refers to a physical stamp or seal used for marking documents or objects. Not commonly used in modern everyday conversation; 印鑑 (いんかん) or スタンプ are more frequent.
この書類には印顆が必要です。
This document requires a stamp.
The word is composed of 印 (いん, 'mark' or 'seal') and 顆 (か, a counter for small round objects). The exact historical derivation is uncertain, but it likely refers to a small seal or stamp.