(idiomatic, location) So as to be hidden from plain view (and thus easily ignored or overlooked).

Used to inquire about the weather. / (by extension, idiomatic) Indicating a change of subject to unimportant topics.

Of sixth rank or order. / (arithmetic) Of, pertaining to, or based on six.

(biochemistry) A polymer of adenylic acid attached to mRNA before transportation to the cytoplasm.