What does Anti-Fit mean?

Slightly oversized pants that look too big or long for wearer.

Heddels explains Anti-Fit

While some prefer a slim, skinny, etc. fit which are designed to complement one’s body/legs, others prefer to have the exact opposite fit, or the Anti-Fit. Also known as baggy and loose.

Additional Resources

An example of Denim Demon Juvvie Raw anti-fit denim:

Raw Denim Term - Anti-Fit