Definition of seacoal:
(n) :
coal from inside the sea: mineral coal that washes up from the sea onto beaches, from which it can be collected and sold.
(n) :
Such coal used in foundry practice, intermixed with foundry sand or applied in a layer on its face, to modify the behavior of the molten metal.
(n) :
(historical, chiefly Southern England) coal from across the sea: mineral coal, as opposed to charcoal, in a time and place in which the former arrived by ship and the latter arrived overland (such as London in Elizabethan times).
(n) :
(historical, technical, chiefly US) coal to be used at sea: a certain class of mineral coal, especially suitable for the steam engines of ships at sea and locomotives.