The Collaborative International Dictionary
obiter dictum \obiter dictum\ ([o^]b"[i^]*t[~e]r d[i^]k"t[u^]m), n.; pl. obiter dicta ([o^]b"[i^]*t[~e]r d[i^]k"t[.a]). (Law), An incidental and collateral opinion uttered by a judge. See Dictum, n., 2 (a) .
Douglas Harper's Etymology Dictionary
Wiktionary
n. An incidental remark; especially (context legal English) a statement or remark in a court's judgment that is not essential to the disposition of the case. (from 18th c.)
WordNet
n. an incidental remark [syn: passing comment]
an opinion voiced by a judge on a point of law not directly bearing on the case in question and therefore not binding [syn: dictum]
Wikipedia
Obiter dictum (more usually used in the plural, obiter dicta) is Latin for a word said "by the way", that is, a remark in a judgment that is "said in passing". It is a concept derived from English common law, whereby a judgment comprises only two elements: ratio decidendi and obiter dicta. For the purposes of judicial precedent, ratio decidendi is binding, whereas obiter dicta are persuasive only.
Usage examples of "obiter dictum".
The judge who sat on Muir and Palmer, the famous Braxfield, let fall from the bench the obiter dictum--'I never liked the French all my days, but now I hate them.
True, Augustus Robb had been considerably more than one over the eight when he had thrown out this obiter dictum, but that did not in any way detract from the value of the pronouncement.