To introduce (something) between other things; especially to insert (possibly spurious) words into a text.
During the course of processing some data, and in response to a directive in that data, to fetch data from a different source and process it in-line along with the original data.
To estimate the value of a function between two tabulated points.
Used other than figuratively or idiomatically: see work, in.
To find time or space for, amid other things.
To work out using a machine in between the sets of someone who is already using that machine.