WordNet sense 1 (the last section of a communication):

close, conclusion, end, ending

WordNet sense 2 (occurring at or forming an end or termination):

final, last, terminal

WordNet sense 3 (the act of closing something):

shutting

WordNet sense 4 (approaching a particular destination; a coming closer; a narrowing of a gap):

closure

WordNet sense 5 (termination of operations):

shutdown, closedown

WordNet sense 6 (a concluding action):

completion, culmination, windup, mop up