teach grandma how to suck eggs

verb1

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To tell an expert how to do things.
- Madam, reply’d Joler, you would have me teach my Grandame to suck Eggs, or set up for a Lent Preacher. — 1707

forms

taught Grandma how to suck eggs · taught grandma how to suck eggs · teaching Grandma how to suck eggs · teaching grandma how to suck eggs · teaches Grandma how to suck eggs · teaches grandma how to suck eggs