The term wakizashi (kanji: 脇差 or 脇指) means "medium-length sword" in English. It is written わきざし in hiragana. It's pronounced roughly like "wah-key-zah-she".
Among non-experts, the wakizashi is known as the medium-length sword that ordinary citizens in the Edo period would carry for protection when going on journeys. There are two ways to write wakizashi, 脇差 being the standardized way. 脇, waki, is an anatomical term referring to one’s side(s). It could also be used as a shortened form of waki no shita, 脇の下, which means one’s armpit(s).
差, which by itself is pronounced sa, means difference. By itself, 指 is pronounced yubi, which means finger. When both kanji are used as verbs, they are pronounced sa. 指し (sashi; infinitive form 指す, sasu) means pointing. 差し (sashi; infinitive form 差す, sasu) can be used to describe various actions, for instance unfolding an umbrella or inserting a plug into an outlet.
Sashi is pronounced zashi in wakizashi due to the linguistic phenomenon called sequential voicing (“S” becomes a “Z” sound). Normally you might expect the word to be rendered as 脇差し, but the hiragana character し (shi) is not required in the writing out of wakizashi.