To greet or receive someone cordially or hospitably upon joining something or entering some place. In this usage, a noun or pronoun can be used between "welcome" and "in." I'd like you all to join me in welcoming Sarah in as our new VP of sales! The foster parents welcomed in the young boy with open arms.
See also: welcome
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.