Origin of the word ad hoc comes from the Latin language. In Latin, it means "for this''. While we use this in the English language we mean "for this specific purpose".
ad hoc meaning
For this specific purpose
Antonyms
Planned, intentional
Synonyms
Extempore, specified, provisional, extemporaneous etc.
Now we know ad hoc meaning, let us use it in sentences to understand its meaning more clearly :
An ad hoc committee was made to take care of tax affairs.
Some ad hoc changes have to be made in the plan at the last moments.
Sometimes it also means spontaneous and unplanned.