If 'A @ B' means 'A is the grandson of B', 'A # B' means 'A is the wife of B' and 'A * B' means 'A is the father of B', then what does '$X\ast Y@Z\#W$ ' mean, if Z has only 1 child?

Let's break down the expressions from right to left:
1. **$Z\#W$ **: Z is the wife of W. (Z is female $female$, W is male $male$, married couple).
2. **$Y@Z$ : Y is the grandson of Z. Since Z and W are married, Y is also the grandson of W.
3. $X\ast Y$ **: X is the father of Y.

Now link with the given condition: "Z has only 1 child".

* Since Y is the grandson of Z, Y must be the child of Z's only child.
* We already know that X is the father of Y.
* Therefore, X must be that only child of Z and W.
* Since W is a male (husband of Z), W is the father of X.