Generalized Zero-Shot Learning (GZSL) methods often assume that the unseen classes are similar to seen classes, and thus perform poor when unseen classes are dissimilar to seen classes. Although some existing GZSL approaches can alleviate this issue by leveraging additional semantic information from test unseen classes, their generalization ability to dissimilar unseen classes is still unsatisfactory. This motivates us to study GZSL in the more practical setting, where unseen classes can be either similar or dissimilar to seen classes. In this paper, we propose a simple yet effective GZSL framework by exploring diverse semantics from external class names (DSECN), which is simultaneously robust on the similar and dissimilar unseen classes. This is achieved by introducing diverse semantics from external class names and aligning the introduced semantics to visual space using the classification head of pre-trained network. Furthermore, we show that the design idea of DSECN can easily be integrate into other advanced GZSL approaches, such as the generative-based ones, and enhance their robustness for dissimilar unseen classes. Extensive experiments in the practical setting including both similar and dissimilar unseen classes show that our method significantly outperforms the state-of-the-art approaches on all datasets and can be trained very efficiently.