Missing is an adjective that refers to something that is absent or cannot be found. Synonyms for missing include absent, lost, vanished, disappeared, and gone. These words can be used to describe a variety of situations, from missing objects and pets to missing persons or lost opportunities. Other possible synonyms for the phrase "be missing" include "be gone," "be lost," or "be misplaced," all of which communicate the same idea of something being absent or unable to be found. Ultimately, the choice of words will depend on context and the desired tone or emphasis, whether it is a serious or more lighthearted situation.