Emasculation of a human male is the removal of the penis and the testicles, the external male sex organs. Removal of the testicles alone is termed castration. Emasculation was a form of punishment in medieval Europe and sometimes formed part of the process of being hanged, drawn and quartered.
By extension, the word has also come to mean to render a male less masculine, including by humiliation, or to deprive anything of vigour or effectiveness. Such metaphorical usage has become much more usual than the literal meaning, e.g., the reduction or removal of legislative enforceability, as in "[William Lewis Hughes] voted for Folkestone’s amendment to Curwen’s emasculated reform bill, 12 June 1809..."
In horticulture, the removal of male (pollen) parts of a plant, largely for controlled pollination and breeding purposes, is also called emasculation.