call to remembrance; keep alive the memory of someone or something, as in a ceremony; "We remembered the 50th anniversary of the liberation of Auschwitz"; "Remember the dead of the First World War"
be or provide a memorial to a person or an event; "This sculpture commemorates the victims of the concentration camps"; "We memorialized the Dead"
mark by some ceremony or observation; "We marked the anniversary of his death"
a splendid assemblage (especially of famous people)
(astronomy) a collection of star systems; any of the billions of systems each having many stars and nebulae and dust; "`extragalactic nebula' is a former name for `galaxy'"