Based on gender stereotypes:
* Masculine: This is the most direct opposite, but it carries a lot of baggage and can be limiting.
* Boyish: This is more playful and less rigid than "masculine".
* Tomboyish: This emphasizes a rejection of traditional feminine traits in favor of more traditionally masculine activities.
Based on aesthetics:
* Edgy: This suggests a more rebellious and unconventional style.
* Androgynous: This focuses on a blurring of traditional gender lines in clothing and appearance.
* Tough: This emphasizes strength and resilience, often through clothing and demeanor.
Based on behavior:
* Serious: This contrasts with the perceived frivolity of "girly".
* Independent: This opposes the stereotype of girls needing to be taken care of.
* Strong-willed: This highlights a sense of agency and self-reliance.
Ultimately, the best opposite for "girly" depends on what you want to communicate. It's important to be mindful of the stereotypes and generalizations associated with each word and to use them thoughtfully.