The Collaborative International Dictionary
Preengaged
Preengage \Pre`["e]n*gage"\, v. t. [imp. & p. p. Pre["e]ngaged; p. pr. & vb. n. Pre["e]ngaging.] To engage by previous contract; to bind or attach previously; to preoccupy.
But he was pre["e]ngaged by former ties.
--Dryden.
Wiktionary
preengaged
vb. (en-past of: preengage)