Synonyms of 'by the way'
▷ See way
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in passing: in chess, said of capturing a pawn that has made an initial move of two squares to its fourth rank, bypassing the square where an enemy pawn on its own fifth rank could capture it. The capture is made as if the captured pawn had moved one square instead of two
He advised her, en passant, that she should see a doctor.
You use incidentally to introduce a point which is not directly relevant to what you are saying, often a question or extra information that you have just thought of.
The tower, incidentally, dates from the twelfth century.
Thesaurus for by the way from the Collins English Thesaurus
You say by the way when you add something to what you are saying , especially something that you have just thought of.