Writer A.S. Byatt once said translators are her best readers. They find every little mistake or typo that even the most meticulous copy editors miss. This isn't because we translators are trying to find mistakes. It's just because we work so closely with the text that we notice problems that editors and even authors can glance over.
We also tend to notice changes in the language before lexicographers get to them. Suddenly a word that always meant X is used in such a way that X can't possibly make sense.
Take the word знаковый, which once meant emblematic but now means — oh, just about anything. To figure out what's up with this adjective, I thought I ought to start with the noun it's from, знак.
Знак doesn't cause too many problems. It is any kind of symbol or sign, like дорожный знак (road sign), or знак качества (sign of quality), or номерной знак (license plate). Знак can be a more figurative sign, like знак дружбы (token of friendship). Or it can be a signal, as in the phrase дай мне знак (give me a sign). It can be a stand-in for money, like денежный знак (bank note or coin). In grammar, it's a kind of punctuation mark, like вопросительный знак (question mark). In your Microsoft Word statistic options, it's a character, as in количество знаков с пробелами (number of characters with spaces). In astrology, it's the thing you are born under, знак Зодиака (Zodiac sign).
Logically, the adjective знаковый would mean symbolic, emblematic, or indicative. And that's what the dictionaries tell you it means, illustrated with a sentence like, Перемены в общественном мнении имеют знаковый характер: они показывают рост консервативных настроений (Shifts in public opinion are emblematic of the rise in conservative views).
But in the late 1980s — specifically 1987, according to Google's N-gram — the word went off the charts in frequency of usage. And it seems to have taken on a new meaning, or maybe several new meanings. In some contexts, the meaning of знаковый seems to have flipped. Instead of describing something or someone that is typical of an era, it describes something or someone that defines an era. So знаковая фигура is a seminal figure, someone who has blazed a trail that others are now following. Он не столько литературная личность, сколько знаковая фигура, которая явно претендует на место новаторов (He's not so much a literary figure as a trendsetter who clearly sees himself among the innovators).
Sometimes знаковый seems to mean "life-changing": Рождение ребёнка — знаковый момент в жизни семьи (The birth of a child is a life-changing event in a family). Бродский — знаковая фигура в моей жизни (Brodsky played a decisive role in my life). Or it apparently means a landmark event or object: Заурядный судебный спор превратился в знаковый процесс (An ordinary lawsuit has turned into landmark court case).
It also seems to be used to describe a significant date or celebration, as if people were thinking of the word значимый (significant) and mixed up their consonants: Знаковый юбилей — нашему заводу 10 лет (A significant anniversary: Our factory is 10 years old).
Lately I've found completely wacko usages — like a competition for знаковый снеговик. What on earth is знаковый снеговик? An emblematic snowman? An influential snowman? A superlative snowman? A landmark snowman? The snowmaniest snowman? If anyone can figure that one out, please let me know.