Ignore (ɪɡˈnɔː)
vb (tr)
to fail or refuse to notice; disregard
n
informal Austral disregard: to treat someone with ignore.
[C17: from Latin ignōrāre not to know, from ignārus ignorant of, from i- in-1 + gnārus knowing; related to Latin noscere to know]
igˈnorable adj
igˈnorer n
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
柯林斯词典应该是正规词典吧。你自己没有查到不能认为就没有。-able这个后缀加在动词之后构成形容词,意为可以被...的,所以ignorable 意为可以被忽略的,表示被动意义。-ant 结尾的形容词为主动意义,表示人无视...的,引申为(人)无知的。