What is a suitable replacement for the SQL Like operator to increase performance?

List<Item> specificItems =
    AllItems.FindAll(i => i.Description.IndexOf(searchString, StringComparison.OrdinalIgnoreCase) >= 0);

Words
-----
chars  | word_id

WordsToEntry
------------
word_id | entry_id

CREATE TABLE WordItemOccurance
(
    [Word] varchar(50) not null,

    ItemId int not null
        constraint FK_Items references ItemTable(ID)
)