To Jolt
Godan verb
ゆさぶる
コウイチが木を揺さぶったので、ビエットは枝に掴まった。
Viet held onto the branch because Koichi shook the tree.
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means shake so the verb vocab version is to shake.
The reading comes from 揺る.