What to call the symbol where there is a break in content or a break in a graph?

Solution 1:

I don't know if this is the official term for it, but I found many results on Google images for the terms graph break and break symbol.

break A zigzag on the line of the x- or y-axis in a line or a bar graph indicating that the data being displayed does not include all of the values that exist on the number line being used. Also called a Squiggle. - Mainland High School, Vocabulary reference maintained by students

Solution 2:

I've seen the terms "scale break" or "axis break", but there are different symbols that can serve this function, as set out in a diagram in this Stack Overflow question: https://stackoverflow.com/q/35627739/8436923

The types of axis break symbol shown in the diagram are: bracket, notch, slantedleft, slantedright, spark, squiggle, and Z.

Also from the documentation for the SAS software: https://blogs.sas.com/content/graphicallyspeaking/2015/09/02/broken-axis-redux/

Many different types of break symbols can be used, such as the "Spark" shown in the graph on the right.