mac·ro·nu·cle·us 
(măk′rō-nklē-əs, -ny-)
(măk′rō-nklē-əs, -ny-)n. pl. mac·ro·nu·cle·i (-klē-ī′)
The larger of two nuclei present in ciliate protozoans, which controls nonreproductive functions of the cell, such as metabolism.
mac′ro·nucle·ar adj.