A handheld extendable rod used to take self-portrait photographs with a smartphone or camera.
I take a selfie stick on trips.
We took a group photo using a selfie stick.
三脚 is a tripod for stable positioning, whereas 自撮り棒 is a handheld monopod for selfies.
Compound of 自撮り (selfie) + 棒 (stick, pole). 自撮り is a relatively recent coinage from 自 (self) + 撮り (taking a photo).