빈말 [bin-mal] empty words
비다 [bi-da] is the infinitive verb meaning “to be empty.” (다 is the equivalent of “to” or “to be”).
Adding a ㄴ (소리 sound) after a vowel-ending adjective turns that adjective into a noun modifier.
말 is the noun for talk or speak.
So 빈말 is empty language, meaning you’re saying something you don’t really mean, you’re saying something that isn’t true, or you’re not going to keep your word.
빈 말 아니예요. [bin-mal a-ni-ye-yo]- I’m not kidding here. (I’m serious.) 빈 말 하지마. [bin-mal ha-ji-ma] – Don’t say something you don’t mean.
(Don’t make promises you’re not going to keep.)