You can't really do that with the basic UI controls in MIDP.
List can't contain TextField.
I would suggest looking at LWUIT since it has better controls.
Otherwise, if you don't need to display Images in your List, then you can use a Form containing both TextField and StringItem. Unfortunately, an ItemStateListener added to the Form will probably not give you as much information as a List.
Implementing the list yourself in a CustomItem means writing quite a bit of code but is doable.
If what you need is a TextField where you enter a search String and a List that displays the search result, I suggest using a TextBox first, then a List. Separate screens are by far the quickest solution here.
Edit: you can't use swing in j2me. what you can do is have just a textfield in a form, then add/remove StringItems to/from the Form when the user changes the content of the TextField. You should be able to rely on ItemStateListener to tell you when the textfield content changes.
Best Answer
You need to elaborate a bit. What kind of a dictionary?
If what you want a list of word pairs, for example to translate between two languages such as English and German, and it is a fairly short list, you could use an in-memory hash table. There is a class Hashtable for this in CLDC. If you need a larger dictionary, you might want to store it on a memory card, and then it gets a bit more complicated to search it. There are also relational databases (such as Mimer SQL Mobile) that can be run under J2ME, and you might look at that option for storage and search.
EDIT:
The original poster added a question as a comment to this answer, about putting a list in a form. This page gives some code examples that might serve as an introduction, although the explanations are in Swedish.