to occupy all the time and attention of (somebody)
to copy or write (something) in large clear handwriting
to prepare the final text of (an official document)
engrosser noun
engrossment noun
[Middle English engrossen from Anglo-French engrosser, prob from medieval Latin ingrossare, from in-2 + grossa large handwriting; (sense 1) French en gros wholesale, ultimately from Latin in in + grossus large]