A bit like psychopathic but not at all like amphitheater. This word seems to only be used for describing chemicals - fatty acids or alpha helices. In these terms, it means that the structure posseses both hydrophobic and hydrophillic groups or atoms. This means that, in bulk, it will tend to assemble into higher structures.

A relevant example are the toxins produced by some bees, which are simple helices (Mellitin, for example - although other insects, frogs and humans cells produce cytotoxic helices). These assemble into pores when they encounter a membrane, allowing free passage of ions - which affects the working of the cell and can pronote cell death.