He's a square

[Puppet]

Hi,

I've heard that expression; ''Don't be such a square".
What that means?

[Atomos]

A square: a boring person, usually because he/she is old-fashioned or works too hard at school.

When someone uses that expression, they really mean, "Stop being so conservative and old-fashioned."

Source: http://www.oxfordadvancedlearnersdictionary.com/dictionary/square
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"I would rather be hated for who I am, than loved for who I am not." Kurt Cobain

[Puppet]

Thank you, Atomos.