Depending on the usage, the opposite of the adverb feverishly could be calmly, or deliberately, or slothfully. Others could be coolly, serenely, or unexcitedly.
calmly
yes feverishly is an adverb. It tells how ex: He wrote feverishly to complete is work on time. feverishly describes how he wrote.
I worked feverishly to get the test completed.
I feverishly layed in bed.
The crew is working feverishly to finish our project on time. She's only spoken feverishly, today.
The people feverishly sent calls for help.
Two main uses I can think of: "Sick and frail, the old man moaned feverishly as he covered himself with a blanket." "The crazy spinster feverishly warned of impending Armageddon to passers by."
synonym
Apparently nowhere....I too have been searching feverishly for the same info.....
The antonym of the word 'synonym' is 'antonym'.
An antonym means "opposite". So an antonym for the word synonym is antonym.
you go down the street and start feverishly blowing as many men as you can.