Sentence:  Unsinkable <WSD>slowed</WSD> and stopped , hundreds of brilliant white flares swayed eerily down from the black , the air raid sirens ashore rose in a keening shriek , the anti-aircraft guns coughed and chattered - and above it all motors roared and the bombs came whispering and wailing and crashing down among the ships at anchor at Bari . 
Meaning of the word marked with <WSD> tags:  lose velocity; move more slowly