Definition of "important"

Thus, when he drew up instructions in lawyer language, he expressed the important words by an initial, a medial, or a final consonant, and made scratches for all the words between. His clerks, however, understood him very well.

1892, Walter Besant, “Prologue: Who is Edmund Gray?”, in The Ivory Gate […], New York, N.Y.: Harper & Brothers, […], page 6

The story struck the depressingly familiar note with which true stories ring in the tried ears of experienced policemen. […] The second note, the high alarum, not so familiar and always important since it indicates the paramount sin in Man's private calendar, took most of them by surprise although they had been well prepared.

1963, Margery Allingham, “Eye Witness”, in The China Governess: A Mystery, London: Chatto & Windus, page 249

For this was the most important thing, that when a person felt strongly about an issue in life, it mustn’t be ignored by others; for if it was, everything subsequent to it would turn out badly, even though there should seem to be no direct connection.

1988, Robert Ferro, Second Son

In plants, the ability to recognize self from nonself plays an important role in fertilization, because self-fertilization will result in less diverse offspring than fertilization with pollen from another individual.

2013 May-June, Katrina G. Claw, “Rapid Evolution in Eggs and Sperm”, in American Scientist, volume 101, number 3

" […] It is a match that must give universal satisfaction. In short, it is a kind of thing that"—lowering his voice to an important whisper—"will be exceedingly welcome to all parties." Recollecting himself, however, he added, "That is, I mean to say—your friends are all truly anxious to see you well settled; Fanny particularly […] "

1811, [Jane Austen], chapter XI, in Sense and Sensibility […], volume I, London: […] C[harles] Roworth, […], and published by T[homas] Egerton, […], page 206