skull and cross-bones

picture of a skull above two crossed bones, once used on the flags of pirates' ships and now to warn of danger, eg on bottles of poison 骷髅画, 骷髅旗（旧时为海盗旗标志, 现作危险标志, 尤用於毒药瓶上）.

skipper, skipping-rope, skirl, skirmish, skirmisher, skirt, skirting-board (Brit) (US `baseboard), skit, skittish, skittishly, skittishness, skittle, skive, skiver, skivvy, Skokie, skua, skulduggery (also skullduggery), skulk, skull, skull-cap, skunk, sky, sky-blue, sky-diver, sky-diving, sky-high, sky-rocket, sky-writing, skylark, skylight, skyline, skyrocket, skyscraper, skywards, slab, slack, slacken, slacker, slackly,