Overflow and piracy transverse drainages involve the dramatic arrival of the trunk drainage downstream of the bedrock high.  This differs from antecedence and superimposition, where the trunk drainage continually flows across the emerging/uplifting bedrock high.  The image below illustrates a pirated drainage where two types of sediment are highlighted.  The sediment derived from the bedrock high in tan and the sediment in green derived from the transverse drainage upstream of the bedrock high.  The contact between the two deposits would be near instantaneous and therefore conformable, and clear evidence for the rapid arrival of an overflow or pirated transverse drainage.