Definition of "frumpy"

Although still young at heart and head, he looks more and more like his old friend Archimedes, increasingly bearded and increasingly grey, with an otherworldly mien – a look that should earn him a spot in the online quiz featuring portraits of frumpy old men under the rubric “Prof or Hobo?”

July 23 2005, Siobhan Roberts, “John Horton Conway: the world’s most charismatic mathematician”, in The Guardian‎