Unkept and unkempt share the broad definition neglected or not properly maintained, but unkempt is usually reserved for describing a person’s rough appearance. The word is derived from the older unkembed, meaning uncombed, and is most appropriate (etymologically considered) in reference to disordered hair.
Unkept, meanwhile, tends to describe neglected properties. Of course, it can also mean simply not kept (usually in reference to promises). Our Microsoft Word spell check catches unkept, but it’s a perfectly good word.
This unkept–unkempt distinction is not a rule, however. Unkempt is often used to describe untrimmed lawns and hedges, for example. Unkept is only rarely used to describe people, but we did find a few instances in our searches.
And, in case anyone is wondering, kempt is indeed a word meaning tidily kept or neatly combed. We assumed the word was obsolete, but, in searching, we actually found a few examples of kempt used in current news publications. It’s usually part of the phrasal adjectives ill-kempt and well-kempt.
His hair is dyed dark and combed in a slightly unkempt manner over one side of his head. [Financial Times]
One woman who is invariably there fits the popular stereotype of the mad, homeless woman with unkempt hair. [New York Times]
It is more or less compulsory for any TV soldier returning to the US from Afghanistan or Iraq to grow a slightly unkempt beard. [Sydney Morning Herald]
The protesters ended their march at a home they said had been foreclosed on by a bank three years ago, and since left unoccupied and unkept. [Wall Street Journal]
The city assessor believes the number of unkept properties around Galesburg has increased so much that the city should be doubling the number of properties flagged for demolition. [Galesburg Register-Mail]
Voters began to grow disenchanted this year with a stagnating economy and unkept promises. [Washington Post]