This use to mean something that is very easy to recall, or something that once learned is quite hard to forget, but as of recent times this is no longer accurate. From now on, in honor of Sleepy Joe Biden, it will be used to refer to a complete fail or an embarrassing mistake, or when somebody forgets something very basic that they should know or something they knew how to do for a long time.
1.
Joe Biden's presidency is just like riding a bike.
2.
I can't believe you forgot the words to that song that you knew by heart all of your life, that was just like riding a bike! Come on man!
Someone who jumps from one relationship immediately into another one.
Serial monogamists can not stand to be alone and often suffer from vast commitment and insecurity issues.
Because they jump into relationships immediately after the previous one has ended, serial monogamists typically don't take the time to reflect on their behavior or why their previous relationships failed; thus, they end up making the same relationship mistakes over and over again.
Person 1: Damn, Dustin already has a new girlfriend?! It's only been two weeks since he broke up with his fiance! I think he's a sociopath.
Someone or something that bites your ankles.
To a postman, an ankle biter is often known as a dog.
To an adult, an ankle biter may be a toddler.
To hikers, an ankle biter is sometimes a tick.
And so on.