I'm surprised no one has really tackled the definition for this one yet! Bolillo is a name for varying kinds of Mexican (white) bread. I disagree with the other definition that states bolillo is a racial slur, however. I've traveled in Central America and Mexico (and Texas, my home) and never got the impression that 'bolillo' was a negative term. It is simply a general term for light-skinned, non-mexicans which may be used in a negative fashion. See 'gringo' and 'guero' for additional related terms.
The previous lexicographer (that's a dictionary writer or contributor) should seriously look into his spouse a bit more. If my girlfriend called me a spic in front of her friends all the time things wouldn't go over to well.
It is not always used in a prejudice way.
"Voy a comprar bolillos para preparar unas tortas."
Oh, and our San Antonio supermarket bakery has a bin labled "Bolillos."
My love. Tu eres mi esposa, mi amor, mi chiquita. Tu eres mi bolillo.