1. come again - Interjection
2. come again - Phrase
(idiomatic, informal, by ellipsis) A polite formula used when one has not heard or understood what has been said, or to indicate surprise.
Synonyms: see Thesaurus:say again
(idiomatic) Used as a polite farewell to a visitor, inviting a return visit.
Source: en.wiktionary.orgThat it shall never come again is what makes life so sweet. Emily Dickinson
A lively understandable spirit Once entertained you. It will come again. Be still. Wait. Theodore Roethke
Exhaust the little moment. Soon it dies. And be it gash or gold it will not come again in this identical guise. Gwendolyn Brooks
If Candlemas day be sunny and bright, winter will have another flight; if Candlemas day be cloudy with rain, winter is gone and won't come again. Darkovan Proverb
Where water has been, water will come again. German Proverb
Rain, rain, go away, come again another day. Traditional Proverb