i Register
In some senses, abuilding is marked as archaic. Watch for register when choosing this word.
adj
Being built or under construction, as a structure or a vessel.
Heere we made a double floore in the hall where the shippe was abuilding, so that the wild men, being ignorant of our way of building, could not take any notice of our cuningnesse, which proved to our desire.
It [the monastery of St. Lawrence in Escorial] cost eight millions; it was twenty-four years abuilding, and the founder himself saw it furnished and enjoyed it twelve years after, […]
Developing or arising, as a trend or an idea.
This may signify much; among other things that the courtesan is creeping into social favor—even that a new code of morals is now abuilding, in which she will be the grand exemplar.