The phrase "wild blue yonders" refers to the vast, open skies above us. Antonyms for this phrase would include terms that describe the opposite of open, wide spaces. These could be words like cramped, confined, or narrow, which suggest a limited or restricted space. Other opposite terms might include words that suggest a lack of freedom or movement, such as stagnant, immobile, or stationary. These antonyms might be used to describe spaces like city streets, crowded rooms, or even small, enclosed areas in the natural world. Alternatively, antonyms could include terms that describe the lower altitudes or ground-level spaces, such as valleys, canyons, or even underground caves.