irresponsible adj.
VERBS be, seem, sound | become | consider sb/sth
ADV. extremely, grossly, highly, terribly, very This was highly irresponsible behaviour. | completely, totally, utterly, wholly He's fun, but totally irresponsible. | rather, slightly, somewhat | socially It is socially irresponsible to refuse young people advice on sexual matters.
You can also check other dicts: irresponsible (English, 中文解释 ), wordnet sense, Collins Definition