An ambitransitive verb (/æmbi:trænzətɪv( v)ɜ:b/) is a verb that has a variable transitivity, so can be used either as a transitively (with a direct object) or an intransitively (without a direct object). That means they can be used in the passive voice.
For example, the English verb "sing" is an ambitransitive verb:
|Transitive, active voice||"Mary sings a song"|
|Passive||"The song was sung (by Mary)"|