Here’s the way I mark the word “altar.” Even though it looks red in the picture, I actually use a brown gel pen to make the outline. The shape gives the impression of the 4 horns of the bronze altar of sacrifice in the Tabernacle. Then I color it in with an orange pencil. (To see my chosen writing instruments, go here.)
If you have a favorite symbol for a common key word found throughout Scripture, feel free to leave a comment. Or email a picture and I will share it!