Answer:
The meaning of the word ambling is to walk or move at a slow, relaxed pace.
The meaning of the word curtail'd is limited or reduced
Explanation:
This excerpt seems to be a self-pitiful and pessimist declaration of a man who believes that he is not attractive in any way and that he came to the world too soon, before being physically finished or formed.
I, that am rudely stamp'd, and want love's majesty
To strut before a wanton ambling nymph;
I, that am curtail'd of this fair proportion
In these four lines he says how unattractive he is to the point that he can not strut his stuff in front of "ambling nymph", that is to say, in front of beautiful and young ladies (perhaps prostitutes) that walk at a slow and relaxed pace.
In the following line, the speaker says that he is "curtail'd" (curtailed) of a fair proportion, with this word, he aims to convey that he has been limited or reduced to a proposition that is not even fair, normal or common.
