A butt plug is specially designed for insertion into the anus. They are different from a regular dildo in that most have a flared base to keep them from slipping too far inside the body. They come in different sizes and shapes, and some vibrate, for added pleasure.
a kind of dildo with a bulge in the center, much like a spindle, so that the shaft gradually thickens, flares out, and then begins to narrow again
a sex toy for insertion into the rectum