If you mean by 'advertise' to make public/proclaim/boast...
then antonyms (opposite words) might be conceal, withhold, depricate.
However there is no antonym for advertise in terms of its commercial use.
The opposite of "advertise" is "conceal" or "hide."
advertise
It's only wise to advertise.
"Advertising" has the root word advertise, from the French "avertir" meaning "To give public notice."
vendo
advertise
Example sentence - My company would advertise in order to increase sales.
what word is opposite of prudent
The opposite of anything is it's absence. Silence would be the opposite of a word spoken.
advertise
three
Opposite word of light
There is no opposite to cobble.