ad lib·i·tum 
(ăd lĭbĭ-təm)
(ăd lĭbĭ-təm)adj.
1. Music At the discretion of the performer. Used chiefly as a direction giving license to alter or omit a part.
2. Of or relating to a diet in which the amount of food is not restricted.
adv.
1. Music At the discretion of the performer: repeat ad libitum.
2. Without restriction; freely: mice that were fed ad libitum.
[Latin ad, according to + libitum, past participle of libēre, to please.]