This is the 12685th most frequent Russian word.
коротком
"Коротком" is the prepositional case, singular form of "короткий," meaning "short" in English.
Defines the 'dress' length as 'short', adjectival usage.
Она предпочитает ходить в коротком платье.
She prefers wearing a short dress.
Describes a 'short' timeframe, attributive usage.
Он говорил о коротком промежутке времени.
He spoke about a short period of time.
Qualifies a 'novel' as 'short', attributive usage.