IPA: /ˌʌn.dɪˈsaɪ.dɪd/
KK: /ʌndɪˈsaɪdɪd/
Not having made a choice or decision about something; not settled or determined.
She felt undecided about which college to attend.
A person who has not yet made a decision or choice, especially in the context of voting or opinions.
The candidates are trying to win over the undecided voters before the election.
Undecided → It is formed from "un-" (meaning not) and "decidere" (from Latin, meaning to cut off or determine). The word "undecided" means not having made a decision or determination.
Think of being 'not' ('un-') able to 'cut off' or determine a choice — that's why undecided means you haven't made a decision yet.