Sizar, one of a class of students at a college of Cambridge University and at Trinity College, Dublin, who, being persons of limited means, are received for lower fees, and obtain free commons, lodgings or other assistance towards their education during their terms of residence. At Oxford there was formerly a similar class, known as Battelers or Batlers, who originally waited on the Fellow of the College who had nominated them, and a still more humble class, the servitors, who, perhaps, answered more to a subsizar at Cambridge.
The name sizar is to be connected with the sizes or sizings (size being a shortened form of assize), that is the specified portions of food and drink issued at a fixed price from the buttery of the college; the sizar was so styled either because as one of his former duties he had to fetch the sizes for others, or because he obtained his own free. The menial duties of sizars at Cambridge have long become obsolete.
Being the entry for SIZAR in the 1911 Encyclopedia Britannica, the text of which lies within the public domain.