what does perpendicular mean?

Perpendicular means two lines (it doesn't even have to be lines, but maybe even rays or line segments)

hit each other at a specific angle in which they produce one or more right angles. That means 90 degrees.

For example, look at a plus sign. +

You can see two lines that are crossing each other and they form four right angles.

one right angle is at the top right, the top left, bottom right, and bottom left.

So, you can say that in a plus sign ( + ), the two lines a perpendicular to each other because they

form 90 degree angles.

Hey! I also noticed that the letter H also has perpendicular lines!

Oh, and the letter T does, too!

And L

and E

and F

my mind is blown.

The angle between two perpendicular lines is 90⁰

Two lines crossing at a 90 degree angle

http://www.mathopenref.com/perpendicular.html