get across也有come across的意思，之外還有被。。。理解壹般用
get it across，get something across，而come across沒有這種用法。只有
your speech/ideas didn't come across.妳沒講清楚明白。
(使)被了解；講清楚，讓…聽懂：
He taught me how to get my ideas across.這裏get不能換成come
他教我如何把自己的觀點表達清楚。
講得清楚明白，可理解；有說服力：
Your speech didn't come/get across; nobody understood your opinion.
妳的演說講得不明不白，沒有人能聽懂妳的意思。
get it across to you把它講清楚，使它被理解
sth come across把它講清楚
sth get across使它被理解
come across更強調講清楚
get across強調被理解