IPA: /ˌdaɪəˈɡræmætɪkəl/
KK: /daɪəˈɡræmɪtɪkəl/
Relating to or represented in the form of a diagram, which is a simplified drawing showing the appearance, structure, or workings of something.
The teacher used a diagrammatical representation to explain the complex process.
Diagrammatical → It is formed from "diagram" (from Greek "diagramma", meaning something drawn or marked out) and "-ical" (meaning pertaining to). The word "diagrammatical" refers to something that is related to or characteristic of a diagram.
Think of a 'diagram' as something that is 'drawn out' to explain ideas, and the '-ical' means it relates to that drawing. So, diagrammatical means relating to the drawing of ideas.