(adj.) extending from right to left; naturally left-handed, but trained to use the right
Derived ultimately from a combination of the Latin words for right (dexter) and left (sinister), in general terms the adjective dextrosinistral merely describes anything moving, extending, or positioned on an axis from right to left. But in certain fields—and in the field of psychology in particular—dextrosinistral is employed in a more specific sense, describing someone who is naturally left-handed, but has been trained against their better instincts to make their right hand their dominant hand. And in particular, someone who has been trained to write with their right hand, rather than their left.
It’s not a word recorded in a great many dictionaries; the earliest record HH could find of this particular term is in a psychological paper dating from 1912, which sought to connect stammering, lisping and other speech impediments to dextrosinistral children. Even at that relatively early date, the bitter consequences of forcing a child to go against their better instincts—seemingly for no other reason than societal preference—seems to have been a cause for concern.