Os is the letter O
Anglo-Saxon Rune Poem (from ragweedforge.com)
The mouth is the source of all language,
a pillar of wisdom and a comfort to wise men,a blessing and a joy to every knight
Os reversed significes challenges with communication, speech and the voice. Being that at this time, the planet Mercury is going in retrograde motion, it seems entirely appropriate that this sign would appear. By the nature of it’s reversed position, Os also gives what I perceive and always found to be the answer to these communication difficulties. Speaking inward, as expressed through reflection, meditation and contemplation, in a sense, taking time to consider what you are going to say, and making sure that what you say is clear, and after saying it, checking in that the communication is clear. All these happen best, when silence is present, and so the need to stop communicating outwardly for a moment, and process what the really needs to be said on the inside.
Of course, a key sign of the lack of these skills is the argument, such as my neighbors are having right now, screaming and shouting and using strong language, which only shows that not only is no one listening to the others, but they are also not listening themselves. Disagreements happen, of course, but to resort to verbal violence shows that communication is being ineffective for all parties involved.