Dumbphone is the opposite of a smart phone. It generally has lower specs than a smart phone in terms of screen size, wireless¹ connectivity, storage space etc. However the critical differentiator² is that there is no development environment that allows any third party applications to be installed (other than java midlets which are very limited). Manufacturers and networks call them 'feature phones'.

Dumbphone就是指“非智能手机”。这类手机通常在屏幕尺寸、无线连接，以及存储空间等参数方面要低于智能手机。不过，两者之间最主要的区别是，非智能手机中无法安装第三方应用程序（java应用除外，不过应用也很有限）。制造商和网络运营商都管这类手机叫做“功能型手机”。

For example:

Your phone is so lame³, it’s a dumbphone.

你的手机太次了，压根不是智能手机。