ひらhiraたいtai
1.

Describing a surface that is smooth and uniform without any noticeable bumps or depressions, indicating a lack of elevation or thickness.

2.

Referring to language or expressions that are straightforward and easy to understand, avoiding complex or formal terminology.

3.

Characterizing a demeanor or attitude that lacks sharpness or harshness, often connoting a gentle and approachable quality.

Example:

古代人たちは地球は平たいと信じていた。