Filter unwanted terms
Not sure what you are exactly looking for. There are many ways to do this. One simple way is like this, 

word_list = ['natural language processing', 'sequential labeling', 'programmable', 'spell checking', 'techniques', 'forensics', 'important issue', 'categorial grammar', 'girls', 'applications']


Since you said, a list of key words,

stopwords = ['programmable','techniques', 'important issue', 'girls', 'applications']

resultwords  = [word for word in word_list if word.lower() not in stopwords]
result = ' '.join(resultwords)

print (result)


This will yield,

&gt;&gt; natural language processing sequential labeling spell checking forensics categorial grammar


Otherwise, if you just have a string of text, use split() method to put each word into a list splitting by space. 

querywords = word_list.split()

resultwords  = [word for word in querywords  if word.lower() not in stopwords]
result = ' '.join(resultwords)


You can always warp them into a function and automate this. As I said there are many ways to do it, without knowing what have you tried, this is a simple way to do without using nltk library.