Opposites:
* Conspicuous: This is the direct opposite, meaning easily seen or noticed.
* Noticeable: Something that draws attention to itself.
* Prominent: Standing out, important, or easily seen.
* Striking: Attracting attention because of being unusual or impressive.
* Obvious: Easily understood or recognized.
Similar meaning, but with a more positive connotation:
* Unassuming: Modest, not trying to attract attention.
* Low-key: Relaxed, understated, and not attracting attention.
* Subtle: Delicate, not obvious or easily noticed.
* Discreet: Careful to avoid attracting attention or causing offense.
More nuanced meanings:
* Hidden: Concealed from view.
* Secretive: Trying to keep something hidden.
* Unremarkable: Not interesting or unusual.
* Plain: Simple and without any special features.
The best word to use will depend on the specific context.