What is Shubhodayam mean?

It is conjugation of two words. Shubha (शुभ)+ udayam (उदयं). Shubha = good or mangalam (मंगलं). Udayam = to rise.When someone wishes or says shubhodayam, then it means let the good or mangalam rise. And, the person who utters also will have a gesture in the form of folded hands nearer to the Heart (not the physical heart) or just a hand touching the Heart. This is a old form of gesture stating that one can be peaceful only when one concentrates on the Heart and not on one's mind or thoughts. This is one way of entering into Silence and wishing the other also to enter into Silence, so that only the Silence prevails (actually awareness of Silence). When the awareness of Silence happens then peace prevails. There is also a Buddhist tradition stating ami tofa  meaning 'let peace be with you'.