The word "interannual" refers to events or changes that happen between one year and another. It describes something that occurs over the course of multiple years or between different years. Full definition
Decadal variations in the North Pacific Gyre Oscillation are characterized by a pattern of sea surface temperature anomalies that resemble the central Pacific El Niño, a dominant mode of interannual variability with far - reaching effects on global climate patterns5, 6, 7. (aer.com)
Cole, J.E., D. Rind, R.S. Webb, J. Jouzel, and R. Healy, 1999: Climatic controls on interannual variability of precipitation δ18O: Simulated influence of temperature, precipitation amount, and vapor source region. (pubs.giss.nasa.gov)
Thus state - of - the - art observations and basic analysis are unable to completely account for recent energy variability at interannual time scales, since they provide either an incoherent narrative or imply error bars too large to make the products useful. (judithcurry.com)