la‧ther1 [singular, uncountable]
a white mass of bubbles produced by mixing soap in water
a white mass that forms on a horse's skin when it has been sweating [= foam]
3 also work yourself into a lather informal
to get very anxious or upset about something:
By the time Alan called, Jody had worked herself into a lather.
very worried, upset, or excited:
He was in a lather of anticipation.