also: くちばっかり
noun
all talk and no action; just words
Describes a person who talks a lot but does not follow through; often used critically. Common in phrases like 口ばかりで何もしない.
彼は口ばかりで、実際には何もしない。
He's all talk and does nothing in reality.
口ばかりの人は信用できない。
You can't trust someone who is all talk.
有言実行 means 'doing what one says', the opposite of 口ばかり; it describes someone who follows through on their words.
Compound of 口 (mouth, speech) and ばかり (only, nothing but). Literally 'only mouth', implying that words are not backed by deeds.