A value of 1 indicates perfect positive correlation — Y goes up in lockstep with X. (realclimate.org)
Correlation is the statistical measure of the degree to which the movements of two variables are related; 1 = perfect positive correlation, 0 = no correlation, and -1 = perfect negative correlation. (franklintempleton.com)
Correlation will range between 1 (perfect positive correlation, moving in the same direction) to -1 (perfect negative correlation, moving in opposite directions). (us.beyondbullsandbears.com)