tedious

An activity or situation that's tedious is boring and annoying because it takes too long or requires too much effort.

When people say something is tedious, they usually mean that it's dragging on for hours, days, or even weeks, and there doesn't seem to be an end in sight. Imagine attending a meeting that lasts three hours without any breaks - you might find it tedious. Or think about doing your taxes every year; it can be such a tedious task because you have to fill out the same forms over and over again. Even some hobbies can be tedious if they require repetition, like knitting a scarf stitch by stitch for dozens of rows.