You are correct. You can use functions like Match() or Pos(). You can use MATCH([Dimension];"*def*")) and this will get you the output and wildcard will match the beginning of the string.
Pos Function is used to return the position of a specific character string.
You can also try using Pos() function as below:
=Pos("def abc ghi";"def")
returns 1
=Pos("def abc ghi";"abc")
returns 5
=Pos("def abc ghi";"xyz")
returns 0
