retreat has 15 distinct synonyms spread across 5 of its 11 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is advance.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
(military) withdrawal of troops to a more favorable position to escape the enemy's superior forces or after a defeat
“the disorderly retreat of French troops”
(military) a signal to begin a withdrawal from a dangerous position
(military) a bugle call signaling the lowering of the flag at sunset
withdrawal for prayer and study and meditation
“the religious retreat is a form of vacation activity”
the act of withdrawing or going backward (especially to escape something hazardous or unpleasant)
make a retreat from an earlier commitment or activity
“We'll have to crawfish out from meeting with him”
Synonyms, antonyms and the broader and narrower relations for retreat come from Princeton University’s WordNet. Full sources and licences.