Read the rest of the post and watch the video and the reference will become clear...
One of the sinks in the master bath has not been draining well recently.
We finally took a few minutes to investigate what was going on.
SWMBO pulled everything out from under the sink while I grabbed a bucket and a pair of slip-joint pliers just in case.
I loosened the trap and emptied into the bucket. The trap was pretty clean.
Then I took off the extension for the tailpiece. It has some goop around its perimeter so I cleaned that out with my finger. The extension is ABS (black plastic) and was cut with a hacksaw so had rough edges protruding on the inside of the pipe. I took a utility knife and trimmed the edges so they were clean and smooth. That should help minimize future issues.
Then I loosened the ball-and-rod for the pop-up drain assembly and removed the rod so I could remove the pop-up stopper. The stopper had a little goop on it, so I cleaned that up too.
Looking down the tailpiece revealed the issue. My fingers aren't long enough to clean it out, So I grabbed a wet wipe and had SWMBO grab a wooden skewer. I balled up the wet wipe and used the skewer to push it down the tailpiece. Here's the result:
I assume it's a coagulated accumulation of makeup, lotion, hair, and other stuff.
We never have to do this with the boys' sinks...