adj. 25B6; adjective
a dreadful accident : TERRIBLE, frightful, horrible, grim, awful, dire; horrifying, alarming, shocking, distressing, appalling, harrowing; ghastly, fearful, horrendous; tragic, calamitous; formal grievous.
a dreadful meal : UNPLEASANT, disagreeable, nasty; frightful, shocking, awful, abysmal, atrocious, disgraceful, deplorable, very bad, repugnant; poor, inadequate, inferior, unsatisfactory, distasteful; informal pathetic, woeful, crummy, rotten, sorry, third-rate, lousy, ropy, God-awful; Brit. informal duff, chronic, rubbish.
you're a dreadful flirt : OUTRAGEOUS, shocking; inordinate, immoderate, unrestrained.
pleasant, agreeable.