Opponent in kata - Terminology used in Japanese MA
I'll start with the word uke since this word was used in the discussion.
In Aikido Aikikai, at the moment, there are two terms that are used to refer to the people performing the technique. First of all, there is uke (受け, うけ) that is 'receiver'* and nage (投げ, なげ), the 'thrower'. However, in earlier books (for example in the first edition of the six-volume work on Aikido by Saito Sensei), the term tori (取り, とり), 'rending', ie 'active partner' is used. Terms tori and uke are to this day used in Judo.
According to Stanly Pranin, Ueshiba Morihei Sensei also used the term shite (probably from 仕手, して - 'protagonist', 'Lead Partner', now a days the term associated with Noh plays) in the pre-war days. I don't believe that this term is used any more in context of Aikido. At least, I've attended a few seminars by direct students of Ueshiba Sensei (Mitsugi Saotome and Yamada Yosemitsu), had a chance to converse with them after the seminars, but at no time did they use the term shite. I kind of wonder what Yoshinkan folks use, since they split off from Aikikai at the earlier time.
Of course, changing terminology indirectly illustrates how the emphasis of Aikido has changed with the times.
In Kendo, the terms uchitachi (打太刀, うちたち) that is 'striking sword' (from utsu, 打つ, うつ - to hit, to strike, to pound) is used to refer to the attacking side, and shitachi (仕太刀, したち)** - 'doing' or 'serving sword' for the defending side. In Jodo/SMR Jojitsu, the term shijo (仕杖, しじょう) is used to denote the kata partner performing the jo side of the kata.
My Iaido Sensei like to use the term teki (敌, てき) - 'the enemy', 'foe', 'threat' to refer to the very enemy that one imagines and then kills during the performance of a iaido kata. "Teki wa doko desuka?" may well be the theme of the lesson on bunkai***. This terminology is used by the ZNKR instructors.
And what are the terms you use to signify the same things?
*: In today's conversational Japanese language, the term 'uke' is more often used as slang denoting a passive homosexual, thanks to proliferation of the yaoi manga. To avoid misunderstandings in conversations with Japanese folks, I was advised to clarify that we are talking about MA.
** Originally it was apparently written 受 太 刀 - 'accepting' or 'receiving sword', the same kanji as used for 'uke', from 'ukeru' (受ける, うける) - 'receive', 'accept'. I've asked a couple of native speakers as to what they think the reading would be, and at least one had an opinion that it's read 'uketachi'. However, one has to bear in mind that young Japanese, especially those not familiar with martial arts, often do not know some of the nuances of the Japanese language.
*** "Teki wa doko desuka" (敵は何処ですか or 敵はどこですか, as 'doko' is seldom written using kanji anymore, since hiragana is faster, てきはどこですか) - 'where (is) the enemy?'. Bunkai (分解, ぶんかい) - 'disassemble', 'analysis', 'deconstruct'.