Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
optimisation is a noun meaning "the act of rendering optimal". It carries one recorded sense.
the act of rendering optimal
“the simultaneous optimization of growth and profitability”
“in an optimization problem we seek values of the variables that lead to an optimal value of the function that is to be optimized”
“to promote the optimization and diversification of agricultural products”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for optimisation come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.