A device for washing or irrigating something, such as a medical syringe or a cleaning appliance. The exact type depends on context.
I cleaned inside my ear with an ear syringe.
This irrigator is used to wash wounds.
nasal irrigation device; nasal rinse bottle
ultrasonic cleaner
Compound of 洗浄 (せんじょう, 'washing, cleaning') and 器 (き, 'device, instrument').