Meaning

• Without humor or expression of happiness; grave in manner or disposition

  "It was a surprise to see the captain, who had always seemed so serious, laugh so heartily."

• Important; weighty; not insignificant

  "This is a serious problem. We'll need our best experts."

• Really intending what is said (or planned, etc); in earnest; not jocular or deceiving

  "After all these years, we're finally getting serious attention."

• (of a relationship) Committed.

Meaning

• In a serious manner; seriously.