cin·der 
(sĭndər)
(sĭndər)n.
1.
a. A small piece of burned or partly burned substance, such as coal, that is not reduced to ashes but is incapable of further combustion.
b. A piece of charred substance that can burn further but without flame.
2. cinders Ashes.
3. cinders Geology See scoria.
4. Metallurgy See scoria.
5. Slag from a metal furnace.
tr.v. cin·dered, cin·der·ing, cin·ders
To burn or reduce to cinders.
[Alteration (influenced by Old French cendre, ashes) of Middle English sinder, from Old English, slag, dross.]
cinder·y adj.