WordNet sense 1 (uninterrupted in time and indefinitely long continuing):

ceaseless, constant, perpetual, unceasing, unremitting, never-ending

WordNet sense 2 (continuing in time or space without interruption):

continuous, uninterrupted

WordNet sense 3 (occurring so frequently as to seem ceaseless or uninterrupted):

endless

WordNet sense 4 (seemingly without interruption; chiefly restricted to what recurs regularly or frequently in a prolonged and closely spaced series):

continual