noun Definition of dot com in Technology (networking) (.com, "commercial") The top-level domain originally for American companies but, since the explosion of the web, used by most companies and for vanity domains of all types, whether in the US or not, often in addition to country code domains like amazon.co.uk. The term "dot com" is now widely used to refer to any Internet business as in "My dot com turned into a dot bomb". 1
