あの大学は私の第1志望だった。
Ano daigaku wa watashi no dai-ichi shibō datta.
That university was my first choice.
大学 (daigaku: university) important + educational institution
私 (watashi: I, me)
第1(dai-ichi: number 1, first)As you may know, 第 is a prefix for ordinal numbers.
志望 (shibō: wish, desire, ambition) ambition + to aspire