The adjective has 2 meanings:
Meaning #1:
likely to spread and cause an epidemic disease
Synonyms: pestilent, pestilential, plaguelike
Meaning #2:
causing irritation or annoyance
Synonyms: annoying, bothersome, galling, irritating, nettlesome, pesky, pestering, pestiferous, plaguy, teasing, vexatious, vexing
The adverb plaguey has one meaning:
Meaning #1:
in a disagreeable manner
Synonyms: plaguy, plaguily
