(adj.) describing a person who looks so grumpy you presume they have a bad temperament
File this one away for future reference. If someone looks drossy, then they look so unpleasant that you presume they must have a terrible attitude as well.
Like the lion’s share of words-you-didn’t-know-you-needed, this is a Scots dialect word, with the definition we posted on Twitter being taken from John Jamieson’s monumental Etymological Dictionary of the Scottish Language (1825).
Speaking of etymology, where does drossy come from? Well, if you look drossy, then put simply you look like dross—a word that has been used to mean ‘dregs’ or ‘refuse’ for nigh on 1,000 years, since the late Old English period at least.
Although we tend to use it generally of any waste material today, dross was originally a more specific term, used to refer to the extraneous scum ejected or left over from the process of smelting metals. By the fifteenth century, that meaning had loosened, so that dross had come to be used of any waste that, due to its being mixed into a finer or more valuable material, renders it useless or impure. So the silt that settles in muddied water, or the sludgy lees left in a vat after fermentation, would be dross.
That looser meaning (an example of a process called ‘semantic widening’, or ‘generalization’ if you want to get all linguistic about it) continued to develop apace over the centuries that followed, so that by the turn of the sixteenth century dross had all but fully established itself as a general term for any waste matter. A handful of more specific meanings remained in use for a time (most notably, as another name for iron pyrites, or fool’s gold), but largely speaking it’s the more general meaning that has survived—and, moreover, inspired the brilliant adjective at the top of this page.