a dull lecture 枯燥无味的演讲 ; 乏味的演讲
dull lecture
乏味的演讲
以上为机器翻译结果，长、整句建议使用 人工翻译 。
The lecture was as dull as ditchwater.
那次讲座非常呆板乏味。
《新英汉大辞典》
The first part of the lecture was vivid but the remaining was dull.
讲座的前半部分很生动，剩下的部分却非常枯燥。
youdao
The lecture was so dull that soon the audience begin to drop away.
演讲单调乏味，不久，听众就开始陆续离席了。
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