I really do not think the 3 line symbol is used much.

An equal sign with a wavy line on top means "Is congruent to". It is used in geometry to say that one shape or angle is the same as another one.

With numbers you say 'equal to'

With geometrical things you say 'congruent to'

http://rapidtables.com/math/symbols/Basic_Math_Symbols.htm

≡ means the same as 

= means equal to 

 

https://answers.yahoo.com/question/index?qid=1006041315789