Definition of "indecorum"

“But in this matter it is you who are to lead. You must set the example,—If others have blunder’d, it is your place to put them right, and shew them what true delicacy is.—In all points of decorum, your conduct must be law to the rest of the party.” This picture of her consequence had some effect, for no one loved better to lead than Maria;—and with far more good humour she answered, “I am much obliged to you, Edmund;—you mean very well, I am sure—but I still think you see things too strongly; and I really cannot undertake to harangue all the rest upon a subject of this kind.—There would be the greatest indecorum I think.”

1814 July, [Jane Austen], chapter XV, in Mansfield Park: […], volume I, London: […] T[homas] Egerton, […], page 293

I hope your eyes are better, but if you must spare them, there is nothing in my pages which a Lady may not read aloud without indecorum, which is more than can be said of Shakspeare.

1823, Charles Lamb, “Letter 305”, in The Works of Charles and Mary Lamb (Vol. 6)‎

This will be done decently and in good order--our training will admit of no indecorum.

1917, Douglas Fairbanks, Laugh and Live‎

Not only were its central personages the patterns of propriety, but no breath of scandal, no shadow of indecorum, might approach its utmost boundaries.

1921, Lytton Strachey, Queen Victoria‎