From Longman Dictionary of Contemporary Englisharmholearm‧hole /ˈɑːmhəʊl $ ˈɑːrmhoʊl/ noun [countable] DCa hole in a shirt, dress, jacket etc that you put your arm through
Examples from the Corpus
armhole• It is therefore possible to measure around an armhole curve and compare the measurement with that of the sleeve head.• She was the hidden double stitching that kept armholes from tearing out.• It fell in soft folds round her neck almost like a cowl collar and the armholes were deep.• Instead of regular shaping at the armhole edge, the decreased stitches seem to be bolder and less frequent.• It can't be used, for example, for casting off a few stitches at the armhole.• Entering the measurements is quite straight forward, except when it comes to the armhole measurement for set-in sleeves.• If you increase this armhole length, increase the width of the sleeve head too.• Stitch sleeves to armhole edges of fronts and back. 