Sentence:  The old nightmare which had caused him so <WSD>many</WSD> wakeful hours came charging in on him once more , only this time he could n't pacify it with a sleeping pill and send it away . 
Meaning of the word marked with <WSD> tags:  a quantifier that can be used with count nouns and is often preceded by `as' or `too' or `so' or `that'; amounting to a large but indefinite number