O was rather difficult to find a word for, so this post will be short and sweet as there isn't much to be said about the topic!
Obiter dictum, also known as Obiter dicta, is a Latin phrase literally meaning 'statement in passing' or 'said in passing'. It is a remark or observation made by a judge that, despite being included in the body of the court's opinion, is not binding and is not essential to the decision.
Under the doctrine of stare decisis, statements which constitute obiter dicta are not binding, however in some jurisdictions such as England and Wales, they can be strongly persuasive.
When looking through cases and judges reasoning, it is often helpful to be able to identify what statements are obiter dicta, and what statements are 'Ratio decidendi'. This means 'the reason' or 'the rationale for the decision', and basically is the principle which the case establishes. The ratio decidendi is the part of the decision which is binding on the lower courts.