This is a strange kanji because it doesn't really mean anything at all. In fact, what it does is it repeats the kanji that comes before it. For example: 人々 is actually 人人. This kanji shows up whenever there's a repeating kanji, because it's often easier to write than writing a more complicated kanji twice. That's why this kanji is the repeater. It repeats what comes before it.
To remember that this kanji is the repeater, though, think of a drop of water dripping into a prison. Drip drop drip drop. It does that over and over again, driving the prisoners nuts. But it never stops. It just repeats over and over.
In Japanese, this symbol is often called the のま because it looks like the katakana characters ノ and マ put together. If you know katakana then this will be easy to read. If you don't, think of it this way:
Your mom is the repeater. She is trying to force feed you over and over again until you explode (literally). You keep yelling "No ma!" (のま) but she doesn't stop. She's on a repeating track, never stopping, repeating forever.
Currently there are no similar looking kanji which exist in the WaniKani learning system