This is the 287th most frequent Slovenian word.
mesecev
"Mesecev" means "of months" in English.
'mesecev' is the genitive plural form of 'mesec' (month), used here to indicate the duration of an activity in terms of months.
Šola traja devet mesecev.
School lasts for nine months.
'mesecev' is in the genitive plural form to quantify the period of waiting that spans multiple months (as indicated by 'več' - several).
Več mesecev sem čakal na odgovor.
I waited for an answer for several months.
'mesecev' appears in the genitive plural to show the period during which something occurred, in this case, a cool breeze (quantified by 'nekaj' - few).