Ambidirectional dominance occurs in a situation where multiple genes influence a phenotype and dominance is in different directions depending on the gene.
The opposite situation, where all genes show dominance in the same direction, is called directional dominance.
[1] In the same example, for both genes A and B increased height is dominant.
According to Broadhurst, ambidirectional dominance is the result of stabilising selection in the evolutionary past.
[1] Ambidirectional dominance has been found for exploratory behaviours in mice[2][3][4] and paradise fish.