If something is definable, you can explain and describe its meaning and exact limits.

definable rules of grammar/syntax 可定义的语法/句法规则

Your office must be a clearly definable space in which no personal activities take place. 你的办公室必须是一个可明确定义的空间，在这个空间里没有私人的活动。

If a word or phrase is definable, you can say what the meaning of it is.

For every definable term in international law there are clear cases and more complicated cases. 国际法中每一个可界定的术语都有明确的案例和更复杂的案例。

The Book Talker has eight hundred and forty-six definable phrases. 《说书人》有八百四十六个可定义的短语。