Depending on context, "dull" can mean bland, stale, tired, banal, ho-hum, murky, muted, faded, muddy, dingy, quiet, faint, blunt, dense, thick, dopey, weary
Sharp
dull
drab
edgeless
Brightest
insipid
brilliant.
blah
throb
tritest
A five letter word for bravery is valor.
A five letter word for "irritate" is "annoy."