"She is not wanting a dress."
Translation:Chan eil i ag iarraidh dreasa.
By itself, nothing, as far as I know. But it's the particle that is used for Gaelic present verbs, equivalent to the English present progressive/present continuous.
That form, brought to the USA by Gaelic-speaking ancestors, survives in some regional varieties of US English, where a speaker might say that some person is "a' comin'" or "a' walkin'", etc.