Good catch. That one went right over my head...
secular: of or relating to the worldly or temporal, not overtly or specifically religious
The Court explicitly noted that even the display of a menorah alongside a Christmas tree might raise additional constitutional questions if located in a public school.
Off topic, but what the heck:
: A sub-group within a culture with traits that distinguish it from the larger culture. Some examples of subculture in American Society are Amish, gays, clergy, Christian Coalitions, Nation of Islam, etc. Secular and religious holidays reflect the variety of subcultures in America. African-Americans celebrate Kwanzaa; Jews, Hanukkah; and Muslims, Ramadan. The Army is a subculture too. It is distinguished by distinctive uniforms, appearance, customs and courtesies, and military jargon. Since many soldiers come from subcultures within the larger society, the need for understanding and respect is obvious.