1An emissary or agent; a representative or proxy. Also (in Jewish worship): a person responsible for leading the communal worship of a synagogue.
In Christian theology sometimes with reference to Jesus as God's representative or emissary.
2A person whose role it is to encourage or support Judaism around the world; especially one assigned to bring Jewish people back to commitment to their faith, or to encourage emigration to Israel.
Mid 19th century. From Hebrew šeli'aḥ messenger, agent, delegate, deputy, in modern Hebrew also specifically denoting a person whose role is to encourage or support Judaism around the world or to encourage emigration to Israel from šālaḥ to send.