What is referred to by 'a coil of yarn'?

Based on the clue 'a cog railroad the first built in the us runs up t...', what is the answer? Based on the clue 'a cogwheel is the symbol of the international asso...', what is the answer? Based on the clue 'a coif de mailles protected this part of the knigh...', what is the answer? Based on the clue 'a coil of hair or a bundle of yarn or cotton', what is the answer? Based on the clue 'a coiled spring is often part of these items that ...', what is the answer? Based on the clue 'a coin honoring the marine corps 230th anniversary...', what is the answer? Based on the clue 'a coin or anything else in this condition is as pe...', what is the answer? Based on the clue 'a coin placed under this vertical sail holder brin...', what is the answer?